bc635VME/bc350VXI
Time and Frequency
Processor
Revision E
User’s Guide
8500-0019
January, 2004
bc635VME/bc350VXI
TIME AND FREQUENCY PROCESSOR
TABLE OF CONTENTS
SECTION PAGE
CHAPTER ONE
INTRODUCTION
1.0 General.................................................................................................................................. 1-1
1.1 Key Features ......................................................................................................................... 1-1
1.2 Physical Overview ................................................................................................................ 1-2
1.3 Specifications........................................................................................................................ 1-3
1.3.1 Time Code Reader .......................................................................................................1-3
1.3.2 Time Code Generator................................................................................................... 1-3
1.3.3 Bus Characteristics ......................................................................................................1-3
1.3.4 Digital Inputs ............................................................................................................... 1-3
1.3.5 External 10MHz Input/Output ..................................................................................... 1-4
1.3.6 Digital Outputs............................................................................................................. 1-4
1.3.7 Oscillator Control Output ............................................................................................ 1-4
1.4 Environmental Specifications ...............................................................................................1-4
1.5 Functional Overview............................................................................................................. 1-4
1.5.1 Time ............................................................................................................................. 1-4
1.5.1.1 Time Sync Mode................................................................................................. 1-4
1.5.1.2 Time Format........................................................................................................ 1-5
1.5.1.3 Set Time.............................................................................................................. 1-5
1.5.1.4 Set Year...............................................................................................................1-5
1.5.1.5 Set Local Offset ..................................................................................................1-5
1.5.1.6 Set Propagation Delay ........................................................................................ 1-5
1.5.1.7 Days ....................................................................................................................1-6
1.5.2 Time Code..................................................................................................................... 1-7
1.5.2.1 Decode ................................................................................................................1-7
1.5.2.2 Generate .............................................................................................................. 1-7
1.5.3 Signals.......................................................................................................................... 1-7
1.5.3.1 Heartbeat (Periodic) Output................................................................................ 1-7
1.5.3.2 Strobe Output...................................................................................................... 1-7
1.5.3.3 Event Input.......................................................................................................... 1-8
1.5.3.4 Frequency Output ............................................................................................... 1-8
1.5.4 Interrupts...................................................................................................................... 1-8
1.5.5 Oscillator Parameters................................................................................................... 1-8
1.5.6 Sync RTC Time to External Time ............................................................................... 1-8
1.5.7 Board Reset.................................................................................................................. 1-8
Symmetricom Inc bc635VME/bc350VXI Time and Frequency Processor (Rev. E) i
TABLE OF CONTENTS
CHAPTER TWO
INSTALLATION AND SETUP
2.0 VME/VXI Compatibility Switches....................................................................................... 2-1
2.1 VMEbus Base Address Selection ......................................................................................... 2-2
2.2 bc350VXI Logical Address Selection .................................................................................. 2-2
2.3 Jumpers ................................................................................................................................. 2-3
2.4 Installation ............................................................................................................................ 2-5
CHAPTER THREE
INTERFACES
3.0 General.................................................................................................................................. 3-1
3.1 Data Input and Output........................................................................................................... 3-1
CHAPTER FOUR
FIFO DATA PACKETS
4.0 General.................................................................................................................................. 4-1
4.1 Writing Data Packets ............................................................................................................ 4-1
4.1.1 Packet “A” - Select TFP Operational Mode ................................................................ 4-2
4.1.2 Packet “B” Set Major Time ......................................................................................... 4-4
4.1.3 Packet “C” Command Input......................................................................................... 4-5
4.1.4 Packet “D” Load D/A Converter ................................................................................. 4-5
4.1.5 Packet “F” Heartbeat (Periodic) Control ..................................................................... 4-6
4.1.6 Packet “G” Offset Control ........................................................................................... 4-9
4.1.7 Packet “H” Set Time Code Format for Mode 0......................................................... 4-10
4.1.8 Packet “I” Clock Source Select ................................................................................. 4-10
4.1.9 Packet “J” Send Data TO GPS Receiver ................................................................... 4-10
4.1.10 Packet “K” Select Generator Code .......................................................................... 4-11
4.1.11 Packet “L” Set Real Time Clock ............................................................................. 4-11
4.1.12 Packet “M” Local Time Offset Select (GPS Modes Only) ..................................... 4-12
4.1.13 Packet “O” Request Data From The TFP ................................................................ 4-13
4.1.14 Packet “P” Path Selection ........................................................................................ 4-15
4.1.14.1 Bit Descriptions .............................................................................................. 4-15
4.1.14.2 Upper Nibble Bit Descriptions ....................................................................... 4-16
4.1.15 Packet “Q” Set Disciplining Gain............................................................................ 4-17
4.1.16 Packet “S” Set Year ................................................................................................. 4-17
ii
bc635VME/bc350VXI Time and Frequency Processor (Rev. E) Symmetricom Inc
TABLE OF CONTENTS
CHAPTER FIVE
PROGRAMMING EXAMPLES
5.0 General.................................................................................................................................. 5-1
5.1 Reading Time on Demand .................................................................................................... 5-1
5.2 External Event Time Capture ............................................................................................... 5-2
5.3 Program Periodic Frequency of 1000 HZ............................................................................. 5-2
5.4 Set Mode 1 and the Major Time ........................................................................................... 5-3
5.5 Select Mode 0 (IRIGB)and Advance TFP 2.5 Milliseconds ................................................ 5-3
CHAPTER SIX
INPUTS AND OUTPUTS
6.0 Inputs and Outputs ................................................................................................................ 6-1
CHAPTER SEVEN
ADJUSTMENTS
7.0 General.................................................................................................................................. 7-1
Symmetricom Inc bc635VME/bc350VXI Time and Frequency Processor (Rev. E)
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TABLE OF CONTENTS
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bc635VME/bc350VXI Time and Frequency Processor (Rev. E) Symmetricom Inc
CHAPTER ONE
INTRODUCTION
1.0 GENERAL
The bc635VME/bc350VXI Time and Frequency Processor User’s Guide provides the following
information:
• Introduction and key feature description.
• Installation and setup.
• Detailed operation and programming interfaces.
• Input and output signals.
• Programming examples.
1.1 KEY FEATURES
The Time and Frequency Processor (TFP) has been designed with the following key features:
• Time on demand (days through 0.1 microseconds) with zero latency. This feature is
implemented with hardware registers which latch the current time upon host request.
• Event logging (days through 0.1 microseconds). This feature is implemented with a second
set of hardware registers. Time is captured on a positive or negative input edge.
• Six operational modes are supported. Modes are distinguished by the reference source.
Mode Source Of Synchronization
Timecode – IRIG-A IRIG-B XR3 2137 NASA 36
0
Free running - on board VCXO used as reference.
1
1 PPS - accepts input one pulse per second.
2
RTC - uses battery backed on board real time clock IC.
3
GPS (optional) - double wide configuration including GPS receiver.
5
(obsolete)
GPS (optional) - uses GPS receiver/antenna (receiver in antenna).
6
Symmetricom Inc bc635VME/bc350VXI Time and Frequency Processor (Rev. E) 1-1
CHAPTER ONE
• Provides an output clock synchronized to the selected reference; programmable 1, 5, or
10MHz TTL.
• All modes of operation are supplemented by flywheel operation. For example, if
synchronization source is lost, the TFP will continue to function at the last known reference
rate.
• Generates synchronized IRIG B timecode. Modulated and DC level shift formats are
produced simultaneously. Also generates IRIG H DC level shift.
• Programmable frequency output (periodics) is provided. The output frequency is 10,000,000
/ (n1 * n2). 1<n1<65536 & 1<n2<65536.
• A time coincidence strobe output is provided. Programmable from hours through
milliseconds. This strobe also has an each second mode programmable to milliseconds.
• Five maskable interrupt sources are supported. IRQ levels one through seven are
programmable.
Int. # Source Of Interrupt
0
1
2
3
4
External event input has occurred.
Periodic output has occurred.
Time coincidence strobe has occurred.
One second epoch (1PPS output) has occurred.
Output data packet is available.
• Time-of-day, hours, minutes, and seconds are displayed on front panel LED's.
• Most inputs and outputs are accessible via the P2 connector.
1.2 PHYSICAL OVERVIEW
The TFP is a B size module (6U X 160 mm). Operation is controlled by a block of thirty-two
D16 registers written and read by the host via the VMEbus (A16 : D16). The TFP is available in
two versions. The bc635VME is intended for use in a VMEbus system with most I/O signals
available on rows A and C of the P2 connector. The bc350VXI is intended for use in a VXIbus
system, and is shipped without a P2 connector. A dip switch is used to select VME or VXI
compatibility. In VMEbus systems the register block can be located on any 64 byte boundary.
In VXIbus systems the register block can be located at any of the 256 logical addresses (A15 and
A14 must be high). The logical address is returned during an interrupt acknowledge cycle.
1-2 bc635VME/bc350VXI Time and Frequency Processor (Rev. E) Symmetricom Inc
1.3 SPECIFICATIONS
1.3.1 TIMECODE READER
INTRODUCTION
Format – AM
Carrier Range
Modulation Ratio
Input Amplitude
Input Impedance
Format - DCLS
Carrier Range
Input Amplitude
Input Impedance
IRIG B XR3 2137 NASA 36.
+/- 50ppm.
3:1 to 6:1.
0.5 to 5 volts peak to peak.
10KΩ AC coupled.
IRIG A IRIG B NASA 36.
+/- 50ppm.
TTL/CMOS Compatible
10KΩ DC coupled.
1.3.2 TIMECODE GENERATOR
Format - AM
Modulation Ratio
Output Amplitude
Format - DCLS
DC Level Shift
IRIG B.
3:1.
0 to 10 volts peak to peak, adjusted by VR1, into 50Ω.
IRIG B IRIG H
TTL/CMOS compatible, into 50Ω.
1.3.3 BUS CHARACTERISTICS
Address Space
Data Transfer
Interrupter
Power
A16, AM codes $29 and $2D, 64 bytes.
D16.
D08(0), I(1-7), ROAK.
+5 @ 1.5amps +12 @ 50 milliamp -12 @ 30 milliamp
1.3.4 DIGITAL INPUTS
Event Capture
TTL/CMOS positive or negative edge triggered.
20 nanoseconds minimum width 250 nanoseconds minimum period.
Input impedance 10KΩ
External 1PPS
TTL/CMOS positive edge on time.
Twenty nanoseconds minimum width.
Input impedance 10KΩ
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CHAPTER ONE
1.3.5 EXTERNAL 10MHz INPUT/OUTPUT
10MHz Input
TTL/CMOS 45% To 55% Duty Cycle.
1.5 To 4 Volts Peak-To-Peak, AC coupled 2.5KHz impedance.
Note: When an ovenized onboard oscillator is used, the external 10MHz input feature is
disabled. Instead the output of the ovenized oscillator appears on this pin. It can only
drive a single high impedance load.
1.3.6 DIGITAL OUTPUTS
1PPS
Periodics
Strobe
1, 5, 10MHz Clock
TTL/CMOS positive edge on time, 200mS positive pulse, into 50Ω.
TTL/CMOS positive edge on time, into 50Ω. (See section 4.1.5)
TTL/CMOS positive edge on time, 1mS positive pulse, into 50Ω.
TTL/CMOS positive edge on time, 5 & 10MHz square wave, 1MHz
80/20 duty cycle, into 50Ω.
1.3.7 OSCILLATOR CONTROL OUTPUT
Control Range
Transfer Coefficient
0 – 5V
Positive
1.4 ENVIRONMENTAL SPECIFICATIONS
Temperature
Operating 0 to 70o centigrade.
Non-Operating -30 to +85o centigrade.
Relative Humidity
Altitude
Operating 85% @ +85 o C, 1000 hours.
Operating -400 to 18,000 meters MSL.
1.5 FUNCTIONAL OVERVIEW
This section describes the functions provided by the bc635VME/bc350VXI Time and Frequency
Processor (TFP).
1.5.1 TIME
This function controls how the TFP card acquires and maintains time data. These functions
allow the user to select where to obtain time data, whether or not to manipulate the time data and
how to present the time data to the user system.
1.5.1.1 TIME SYNC MODE
This allows the user to select the operating mode (time source) of the TFP device. Available
modes are Time Code Decoding, Freerunning, External 1PPS, RTC & GPS (Optional).
1-4 bc635VME/bc350VXI Time and Frequency Processor (Rev. E) Symmetricom Inc
INTRODUCTION
1.5.1.2 TIME FORMAT
The event time capture and time registers of the TFP default to the decimal time format. The
major time registers are divided into 4 bit fields for each decimal digit of days, hours minutes
and seconds. For the GPS mode only, the time registers can operate in the binary format where
major time is represented as seconds since the GPS epoch.
1.5.1.3 SET TIME
This function allows the user to set the time on the TFP device. Decimal time values can be
entered into the time registers. This function is typically used when operating in either the
Freerunning or External 1PPS modes. While the function may be used when operating in Time
code or GPS modes, subsequent time data received from the selected reference source will
overwrite the loaded time.
1.5.1.4 SET YEAR
This function allows the user to set the year data. Typically, this function is used when the board
is operating in time code decoding mode. Many time code formats (including standard IRIG B)
do not include year information in the data. Using this function will allow the TFP device to
extract the time of year data from the time code source while using year information provided by
the user. The board will decode the year and roll over the days for a leap year (365-366-001) or a
non-leap year (365-001). The supported range is 1990 – 2037. The board will follow the input
time source if the input rollover day sequence does not match the board rollover day sequence as
defined by the programmed year.
1.5.1.5 SET LOCAL OFFSET
This function allows the user to program a local offset of 1-hour increments into the TFP device.
If the local offset value is nonzero, the device will adjust any reference timing information in
order to maintain a local time in TFP clock. Use of this function only affects the time data in the
TIME registers described in paragraph 3.1.
1.5.1.6 SET PROPAGATION DELAY
This function allows the user to command the TFP device to compensate for propagation delays
introduced by the currently selected reference source. For example, when the unit is operating in
Time code decoding mode, a long cable run could result in the input time code having a
propagation delay. The delay value is programmable in units of 100ns and has an allowed range
from –9999999 through +9999999.
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CHAPTER ONE
1.5.1.7 DAYS
When a time source signal is not present at board power up, the board will begin counting at day
000. The TFP can be operated to count days in two modes. For the default Day 000 Invalid
Mode, the TFP will not accept an input day of 000. Table 1 shows the possible combinations of
input source data and current board state on the left side, and the result of the day rollover on the
right side. Note that the table includes such combinations as where the board is set to a non-leap
year, but the source is in a leap year.
Table 1 Day 000 Invalid Mode
Combination
number
1.1.1 99 Timecode N/A 000 99 Freerun lost track
1.1.2 99 Timecode 99 365 – 001 99 - 00 365 – 001
1.1.3 99 Timecode 00 366 – 001 99 - 00 366 – 001
1.2.1 99 Freerun N/A 365 99 - 00 365 – 001
1.2.2 99 Freerun N/A 366 99 - 00 366 – 001
2.1.1 00 Timecode 00 365 – 366 00 365 – 366
2.1.2 00 Timecode 99 365 – 001 00 365 – 001 1
2.1.3 00 Timecode 00 366 – 001 00 - 01 366 – 001
2.2.1 00 Freerun N/A 365 00 365 – 366
2.2.2 00 Freerun N/A 366 01 366 – 001
Note 1: Day went to 366 for about one second, then went to day 001
Board
year
Input mode Source
Year
Source day Board year Board day Notes
For the optional Accept Day 000 Mode, the TFP will accept an input source with an input day of
000. Table 2 shows the possible combinations for this mode.
Table 2 Accept Day 000 Mode
Combination
number
3.1.1 99 Timecode N/A 000 99 000 – 001
3.1.2 99 Timecode 99 364 – 365 99 364 – 365
3.1.3 99 Timecode 99 365 – 001 99 – 00 365 – 001
3.1.4 99 Timecode 00 365 – 366 99 – 00 365 – 366
3.1.5 99 Timecode 00 366 – 001 99 – 00 366 – 001
3.2.1 99 Freerun N/A 000 99 000 – 001
3.2.2 99 Freerun N/A 364 99 364 – 365
3.2.3 99 Freerun N/A 365 99 – 00 365 – 000
3.2.4 99 Freerun N/A 366 99 – 00 366 – 000
4.1.1 00 Timecode N/A 000 – 001 00 000 – 001
4.1.2 00 Timecode 00 365 – 366 00 365 – 366
4.1.3 00 Timecode 00 366 – 001 00 – 01 366 – 001
4.1.4 00 Timecode 99 365 – 001 00 365 – 001
4.2.1 00 Freerun N/A 000 00 000 – 001
4.2.2 00 Freerun N/A 365 00 365 – 366
4.2.3 00 Freerun N/A 366 00 - 01 366 – 367
Note 2: Day went to 000 for about one second, then went to day 001
Board
year
Input mode Input Year Input day Board year Board day Notes
2
2
2
2
2
2
1.5.2 TIME CODE
1-6 bc635VME/bc350VXI Time and Frequency Processor (Rev. E) Symmetricom Inc
INTRODUCTION
This function group provides access to functions controlling TFP card operation while decoding
time code. These functions allow the user to control both the time code decoding and time code
generating circuits of the device.
1.5.2.1 DECODE
This function allows the user to select the format and modulation types associated with an input
timing signal. These values control how the device attempts to decode the input time code.
These values may be set regardless of the mode but will only be used in time code decoding
mode. The format defines the type of the time code data. The modulation defines the envelope
for the signal and which input pin the signal will be extracted from. The default format is IRIG
B and the default modulation envelope is AM (amplitude modulated).
1.5.2.2 GENERATE
This function allows the user to select the format of the time code that will be generated by the
TFP device. The time code generator supports IRIG B and IRIG H DCLS.
1.5.3 SIGNALS
This group provides access to functions that control various hardware timing signals either
decoded or generated by the TFP card.
1.5.3.1 HEARTBEAT (PERIODIC) OUTPUT
This function allows the user to command the TFP to produce a clock signal at a specified
frequency. The heartbeat signal, also referred to as a periodic, can be either synchronous or
asynchronous to the internal 1PPS epoch in the TFP device. This functionality is implemented
in hardware on the TFP device by an Intel 82C54 counter timer chip. The heartbeat circuit has
two 16 bit divisors, which are clocked by the counter. As the output of the first divisor provides
the clock for the second divisor, manipulating the divisor values results in various duty cycles.
The output of this circuitry is capable of creating a VME bus interrupt. See Section 4.1.5 for a
description of how to program the heartbeat output.
1.5.3.2 STROBE OUTPUT
This function allows the user to command the TFP to produce a hardware signal at a particular
time, or at a particular point during a 1 second interval. When major/minor mode is selected, a
hardware signal will be produced when the internal time of the TFP device matches the values
entered for the major and minor strobe registers. The major time in hours, minutes and seconds
may be supplied in addition to the milliseconds loaded in the minor strobe register. When minor
mode is selected, a strobe signal is produced every second when the internal millisecond count in
the TFP device matches the value entered in the minor strobe register. The output of this
circuitry is capable of creating a VME bus interrupt.
Symmetricom Inc bc635VME/bc350VXI Time and Frequency Processor (Rev. E) 1-7
CHAPTER ONE
1.5.3.3 EVENT INPUT
This function allows the user to command the TFP device to monitor a hardware timing signal.
The source for the signal can be either the External Event input on the device or the output of the
Heartbeat (Periodic) mentioned earlier in this chapter. The External Event signal capture may be
set to occur on either the rising or falling edge. The Heartbeat signal capture is always on the
rising edge. When a signal occurs in the selected format, the time at which the signal occurred is
loaded into the event time registers. The capture lockout checkbox can be used to control
whether or not subsequent signals will overwrite the data in the event time registers. The output
of this circuitry is capable of creating a VME bus interrupt.
1.5.3.4 FREQUENCY OUTPUT
This function allows the user to control the frequency signal output by the TFP device. The
available frequencies are 1, 5 and 10 MHz. The default state of this output is 10MHz.
1.5.4 INTERRUPTS
This function allows the user to control the generation of VME bus interrupts by the TFP device.
If the latch event time function is enabled, the TFP will latch the time in the event time registers
when an interrupt is detected. The user may query the event time registers to see when a
particular event occurred. The latch event time function should not be enabled when external
events are selected as these already latch the time in the event registers. Three control registers
are provided to control the VME interrupts.
1.5.5 OSCILLATOR PARAMETERS
This group allows the user to select an external oscillator or the on board oscillator, in addition
to enabling/disabling disciplining and jamsyncing. If disciplining and jamsyncing are disabled,
the oscillator control DAC can be programmed to hold the oscillator control voltage to a specific
value. When the TFP is synchronized to an input time source, the oscillator will be disciplined to
the input source signal.
1.5.6 SYNC RTC TIME TO EXTERNAL TIME
This function allows the user to force the Real Time Clock (RTC) time to the board time.
1.5.7 BOARD RESET
This function allows the user to reset the TFP device. This command is useful when starting a
test or in the case that unexpected behavior is observed from the card. This function is not used
during normal operation.
1-8 bc635VME/bc350VXI Time and Frequency Processor (Rev. E) Symmetricom Inc
CHAPTER TWO
INSTALLATION AND SETUP
2.0 VME/VXI COMPATIBILITY SWITCHES
The TFP is designed for both VMEbus and VXIbus compatibility. Switches SW2-3 and SW2-4
are used to select the bus protocol. To select VXIbus compatibility set SW2-3 and SW2-4 to the
OPEN or OFF position. To select VMEbus compatibility set SW2-3 and SW2-4 to the CLOSED
or ON position.
SW1 and SW2 Location
Revision A Through Revision D
1
SW1
8
P1
1
SW2
4
P2
Figure 2-1 Address Switches
SW1 and SW2 Location
Revision H
1
SW1
8
1
4
P1
SW2
P2
Switch SW2-3 controls the register block addressing within the A16 address space. With this
switch in the VXI position, address bits A14 and A15 must be one for A16 selection. Switch
SW1 is then used to select the logical address for the module. With SW2-3 in the VME position,
the module can be mapped to any 64 byte block in the A16 address space. SW2-1 and SW2-2
set the A14 and A15 address bits, and SW1 is used to set the A13 through A6 address bits.
Switch SW2-4 controls the status/ID byte returned during interrupt acknowledge cycles. With
SW2-4 in the VXI position, the Status/ID byte returned during interrupt acknowledge cycles is
the logical address set with SW1. When SW2-4 is in the VME position, the Status/ID byte
returned during interrupt acknowledge cycles is the user programmable vector loaded into the
VECTOR register (discussed in Chapter Three).
Symmetricom Inc bc635VME/bc350VXI Time and Frequency Processor (Rev. E) 2-1
CHAPTER TWO
2.1 VMEbus BASE ADDRESS SELECTION
Base address selection for the VMEbus requires the setting of switch SW1 (A6 through A13) and
SW2 (A14 and A15). The bc635VME occupies 64 bytes in the A16 address space and can be
freely located on any 64 byte boundary. The correspondence of the switch positions to the
address bits is illustrated in Table 2-1.
Table 2-1
Address Bits Switch Positions
SW2 SW1
Address Bit A15 A14 A13 A12 A11 A10 A09 A08 A07 A06
Switch Number 2187 654321A16 address range used.
(The BASE address is
on the left side.)
Example switch
00000000000x0000 - 0x003F
settings for SW1
and SW2.
1 = OPEN or
00000000010x0040 - 0x007F
OFF
0 = CLOSED or
00000000100x0080 - 0x00BF
ON
00000000110x00C0 - 0x00FF
00000001000x0100 - 0x013F
………………………… …
………………………… …
11111110110xEFC0 - 0xFEFF
11111111000xFF00 - 0xFF3F
11111111010xFF40 - 0xFF74
To select a base address, set each of the switches to the logical zero (CLOSED or ON) or the
logical one (OPEN or OFF) state.
2.2 bc350VXI LOGICAL ADDRESS SELECTION
Logical address selection for the VXIbus requires the setting of switch SW1 (A6 through A13).
The bc350VXI occupies 64 bytes in the A16 address space and can be located at any of the 256
logical addresses within the VXIbus. The correspondence between the switch positions and the
address bits, and the logical state corresponding to a switch setting follows the description
provided in Section 2.1
2-2 bc635VME/bc350VXI Time and Frequency Processor (Rev. E) Symmetricom Inc
INSTALLATION AND SETUP
2.3 JUMPERS (DEFAULT SETTING IN BOLD TYPE)
The jumper locations for the Rev. A through Rev. F TFP versions are shown in Figure 2-2. The
Rev. G and up along with the P100004 version jumpers are shown in Figure 2-3. The jumper
blocks are not drawn to scale in order to make the numbers more visible. It may be helpful to
refer to the schematic diagrams to obtain a clearer idea of the function of each jumper option.
JP1
With the jumper in the 1-2 position the TFP is configured to use DC level shift input timecode.
In the 3-4 or open position the TFP is configured to use modulated timecode.
JP2 (GPS Option)
In the 1-2 position the TFP is configured to use a single ended 1pps GPS input. In the 3-4
position the TFP is configured to use a differential 1pps GPS input.
JP3 (GPS Option)
In the 1-2 position the TFP is configured to use the ACUTIME Smart Antenna or SV-6 as the
GPS sensor. In the 3-4 position the TFP is configured to use the TANS as the GPS sensor.
The ACUTIME, SV-6, and TANS are GPS sensor options that are available from Symmetricom,
Inc. This jumper is not present on the P100004 model boards.
JP4
The jumpers in the JP4 group are designed to be moved as a pair. Positions 3-4 and 5-6 define
one configuration, and positions 1-2 and 7-8 define a second configuration. In the default
configuration the TFP is configured with an auxiliary RS-422 output. In the second
configuration the TFP is configured in a daisy-chain mode (the RS-422 input is jumpered to the
RS-422 output). This jumper set is intended to be used in a digital synchronization mode. At the
present time this mode has not been implemented. This jumper is not present on the P100004
model boards.
JP5
In the 1-2 position this jumper places a “100Ω” load between the RS-422 input lines. In the 3-4
position the “100Ω” load is bypassed. When the TFP is the terminal device on an RS-422 daisy
chain the load should be used. When the TFP is not at the end of the chain the load should be
omitted.
JP6
In the 1-2 position this jumper places GROUND on P2 pin C12. In the 2-3 position the 1, 5,
10MHz clock is driven out of P2 pin C12. On the model P100004 boards, this jumper is
implemented as a 2x2 pin block. A shunt on pins 2 and 4 enables the 10MHz output on P2 pin
C12. A shunt on pins 1 and 2 disables the output by grounding P2 pin C12.
Symmetricom Inc bc635VME/bc350VXI Time and Frequency Processor (Rev. E) 2-3
CHAPTER TWO
Jumper Location
Revision A and Revision B
1
34
1
34
2
JP2
2
JP1
P1
P2
Jumper Location
Revision D Through Revision F
JP2
JP1
JP3
2
1
34
1
34
2
2
1
34
1
34
1
34
2
JP5
2
JP4
P1
P2
Jumper Location
Revision G and Up
1 2
34
JP2
1
34
JP1
1
34
JP3
1
34
1
34
2
123
JP6
2
Figure 2-2 Jumper Locations I
2
JP5
2
JP4
P1
P2
Jumper Location
P100004 Models
1 2
34
JP2
1
34
JP1
1 2
34
2
1
34
JP5
P1
2
JP6
P2
Figure 2-3 Jumper Locations II
2-4 bc635VME/bc350VXI Time and Frequency Processor (Rev. E) Symmetricom Inc
INSTALLATION AND SETUP
2.4 INSTALLATION
To install the TFP into a computer chassis follow the steps below.
• Remove the IACKIN*/IACKOUT* back plane jumper for the TFP slot. This step should be
performed even if TFP interrupts are not used.
• bc635VME users must verify that signals on rows A and C of the P2 connector are not used
for VSB or other purposes. The TFP provides signal I/O on rows A and C that may produce
a conflict. If a conflict does exist, a solution is to obtain a bc635VME with the P2 connector
removed.
• Verify that power is off and insert the TFP into the chassis, securing it in the slot by
tightening the two front panel screws.
Symmetricom Inc bc635VME/bc350VXI Time and Frequency Processor (Rev. E) 2-5
CHAPTER TWO
This Page Intentionally Left Blank.
2-6 bc635VME/bc350VXI Time and Frequency Processor (Rev. E) Symmetricom Inc
CHAPTER THREE
INTERFACES
3.0 GENERAL
The TFP occupies 64 bytes in the VMEbus/VXIbus, A16 address space. Refer to Section 2.1 for
details on VMEbus Base Address selection, and to Section 2.2 for VXIbus logical address
selection. TFP data transfers are D16 with the exception of packet I/O which allows D08(0)
transfers. A glossary of key terms commonly used in the discussion of timing operation is
provided below.
Epoch
A reference time or event. Epoch often refers to a one pulse per second event.
Flywheel
Maintain time or frequency accuracy as well as local resources when a time or frequency
reference has been lost or removed.
Periodic
A programmable frequency which is obtained by dividing the TFP reference frequency.
Periodics are sometimes referred to as “heartbeats.” Periodics may optionally be synchronous
with the 1pps epoch if the period is expressible as a ratio of integers.
Major Time
Units of time larger than or equal to seconds. A day hr:min:sec format is usually implied.
Minor Time
Subsecond time to whatever resolution is supported.
Packet
A group of bytes conforming to a defined structure. Packets are usually used in bit serial or byte
serial data transmission to allow framing of the transmitted data.
3.1 DATA INPUT AND OUTPUT
Communication with the TFP is performed using a set of memory mapped registers. These
registers may be read only (R), write only (W), or read/write (R/W). In some cases a read/write
register is structured to support dissimilar data in the read and write directions. Table 3-1
summarizes the type of register located at each hexadecimal offset, and provides a brief
description of the register function. The data format and detailed descriptions of each register
are provided in the next section.
Symmetricom Inc bc635VME/350VXI Time and Frequency Processor (Rev. E) 3-1
CHAPTER THREE
Table 3-1
TFP Register Map Summary
HEX Offset Type Label Function Read/Write
0 R ID Register. VXIbus ID Register
2 R Device. VXIbus Device Type Register
4 R/W Status/Control. VXIbus Status / Control Registers
6-08 Reserved
0A R TIMEREQ Time Request (Time Latching Strobe)
0C R TIME0 Requested Time (includes status byte)
0E R TIME1 Requested Time
10 R TIME2 Requested Time
12 R TIME3 Requested Time
14 R TIME4 Requested Time
16 R EVENT0 Event Time
18 R/W EVENT1 / STROBE1 Event Time/Strobe Time
1A R/W EVENT2 / STROBE2 Event Time/Strobe Time
1C R/W EVENT3 / STROBE3 Event Time/Strobe Time
1E R EVENT4 Event Time
20 R/W UNLOCK Release Lockout/Capture Time
22 R/W ACK Acknowledge Register
24 R/W CMD Command Register
26 R/W FIFO FIFO Input/Output (D16 or D08[O])
28 R/W MASK Interrupt Mask
2A R/W INTSTAT Interrupt Status
2C R/W VECTOR Interrupt Vector
2E R/W LEVEL Interrupt Level
30-3E Reserved
Offset 0x00 ID REGISTER Reset Value 0xXef4
This register was implemented to satisfy the VXIbus Specification. Bit assignments are as
follows.
Table 3-2
Bit # 15-14 13-12 11-0
Use Of Field Device Class Addressing Modes Manufacturer's ID
TFP Meaning Register Based * A16 Only * 0xef4
* Bits 12-15 are not driven high during a read of the ID Register. In most cases they will float
high during a read cycle.
3-2 bc635VME/bc350VXI Time and Frequency Processor (Rev. E) Symmetricom Inc
INTERFACES
Offset 0x02 DEVICE Reset Value 0xX350
This register simply contains (in the case of an A16 only device) a manufacturer's card ID. Bits
12-15 are not driven high during a read of the Device Register. In most cases they will float high
during a read cycle.
Offset 0x04 STATUS Reset Value 0xffff
The TFP does not support VXIbus initialization and diagnostic features. The reset value is
always returned.
Offset 0x04 CONTROL Reset Value 0xfffe
Writing to this register with bit 0 set will deassert any pending interrupts and will clear all used
bits in offsets 0x20 through 0x2E (except FIFO at offset 0x28). Writing to this register with bit
zero cleared has no effect. All other bits are ignored during a write.
Offset 0x0A TIMEREQ Reset Value NA
Reading this register latches the current time and status into offsets 0x0C through 0x14. The
value read is indeterminate.
* * * WARNING * * *
Many compilers will optimize out of existence an assignment made to a local variable if that
variable is not used. For example, the following code snippet may not read offset 0x0A.
timeptr = (short *)(BASE + 0x0A) ; /* initialize pointer */
local_dummy = *timeptr++ ; /* latch the time ?? */
read_time(timeptr) ; /* read the time */
The following form is recommended. Use of the global prevents optimizing out.
timeptr = (short *) (BASE + 0x0A) ; /* initialize pointer */
global_dummy = *timeptr++ ; /* latch the time */
read_time(timeptr) ; /* read the time */
Offset 0X0C TIME0 Reset Value NA
Offset 0X0E TIME1 Reset Value NA
Offset 0X10 TIME2 Reset Value NA
Offset 0X12 TIME3 Reset Value NA
Offset 0X14 TIME4 Reset Value NA
For clarity the above offsets have been grouped.
Symmetricom Inc bc635VME/bc350VXI Time and Frequency Processor (Rev. E) 3-3
CHAPTER THREE
Table 3-3
Bit # 15-12 11-8 7-4 3-0
TIME0 Field
TIME1 Field
TIME2 Field
TIME3 Field
TIME4 Field
Not Defined Not Defined Status (Note 1) Days Hundreds
Days Tens Days Units Hours Tens Hours Units
Minutes Tens Minutes Units Seconds Tens Seconds Units
10E-1 Seconds 10E-2 Seconds 10E-3 Seconds 10E-4 Seconds
10E-5 Seconds 10E-6 Seconds 10E-7 Seconds Not Defined
Offset 0x16 EVENT0 Reset Value NA
Offset 0x18 EVENT1 Reset Value NA
Offset 0x1A EVENT2 Reset Value NA
Offset 0x1C EVENT3 Reset Value NA
Offset 0x1E EVENT4 Reset Value NA
For clarity the above offsets have been grouped.
Table 3-4
Bit # 15-12 11-8 7-4 3-0
EVENT0 Field
EVENT1 Field
EVENT2 Field
EVENT3 Field
EVENT4 Field
Not Defined Not Defined Status (Note 1) Days Hundreds
Days Tens Days Units Hours Tens Hours Units
Minutes Tens Minutes Units Seconds Tens Seconds Units
10E-1 Seconds 10E-2 Seconds 10E-3 Seconds 10E-4 Seconds
10E-5 Seconds 10E-6 Seconds 10E-7 Seconds Not Defined
Note: bit 6 1 = frequency offset > 5E7 in Mode 0 0 = frequency offset < 5E7 in Mode 0
1 = frequency offset > 5E8 0 = frequency offset < 5E8
bit 5 1 = time offset > X microseconds 0 = time offset < X microseconds
(X = 5 for mode 0 X = 2 more all other modes)
bit 4 1 = flywheeling (not locked) 0 = locked to selected reference
Offset 0x18 STROBE1 Reset Value 0xXX00
Offset 0x1A STROBE2 Reset Value 0x0000
Offset 0x1C STROBE3 Reset Value 0x0000
For clarity the above offsets have been grouped.
3-4 bc635VME/bc350VXI Time and Frequency Processor (Rev. E) Symmetricom Inc
INTERFACES
Table 3-5
Bit # 15-12 11-8 7-4 3-0
STROBE1 Field
STROBE2 Field
STROBE3 Field
Not Defined Not Defined Hours Tens Hours Units
Minutes Tens Minutes Units Seconds Tens Seconds Units
10E-1 Seconds 10E-2 Seconds 10E-3 Seconds Not Defined
Offset 0x20 UNLOCK Reset Value NA
A read of this register releases the time capture lockout function if it has been enabled. See
“CMD OFFSET 0x24” for additional details. The data read from this offset is meaningless. A
write to the UNLOCK register acts as a secondary time latching strobe. Time is latched in
EVENT0 - EVENT4. This feature allows the host to capture two times independently.
Offset 0x22 ACK Reset Value 0xXX00
Table 3-6
Bit # Control Function (SET = “1” = High Voltage, CLEAR = “0” = Low Voltage)
0
1
2
3
4
5
6
7
8-15
TFP
HOST
SETS bit to acknowledge the receipt of a valid input packet from host
CLEARS bit by writing to this register with bit 0 SET.
Reserved
TFP
HOST
SETS bit when output FIFO contains a data packet.
CLEARS bit by writing to this register with bit 2 SET.
This bit can generate an interrupt. (see OFFSET 0x2A INTSTAT).
Reserved
TFP
HOST
SETS bit if output FIFO contains data. CLEARS bit if output FIFO empty.
CLEARS output FIFO by writing to this register with bit four SET.
Reserved
Reserved
HOST Must write to this register with bit seven SET to cause TFP to take action
on the data packet previously written to the input FIFO.
Reserved
Symmetricom Inc bc635VME/bc350VXI Time and Frequency Processor (Rev. E) 3-5
CHAPTER THREE
Offset 0x24 CMD Reset Value 0xXX00
This register is used to command the TFP to perform specific functions.
Table 3-7
Bit # Name Function
LOCKEN Event capture lockout (0 = disable lockout 1 = enable lockout).
0
Prevents a new event from overwriting a previous event until an
UNLOCK is performed (see OFFSET 0x20 UNLOCK).
HBEN Enable periodic time capture (0 = disable 1 = enable).
1
When enabled the periodic output is logically OR'ED with the event
input, and the time of the periodic may be read in EVENT0 - EVENT4.
EVSENSE Event capture sense select (0 = rising edge 1= falling edge).
2
EVENTEN Event capture enable (0 = disable 1 = enable).
3
STREN Time coincidence output strobe enable (0 = disable 1 = enable).
4
STRMODE Strobe mode (0 = use major and minor time 1 = use minor time only).
5
In mode (1) an output strobe is produced each second.
6
7
8-15
FREQSEL0 0 10
MHz
FREQSEL10011
15
MHz
Reserved
01
MHz
11
MHz
Offset 0x26 FIFO Reset Value NA
Reads take data from the output FIFO. Writes place data into the input FIFO. Both the input
FIFO and the output FIFO may also be accessed via D08(O) at offset 0x27. Each FIFO has a
depth of 512 bytes.
Data must be written to and read from the FIFO in the following data packet format.
byte 1 0x01 header byte (ASCII SOH)
byte 2 “A” through “Z” idbyte (defined in Chapter Four)
byte 3 data always ASCII i.e. 0 = 0x30
byte 4 data
. . the number of data bytes varies
byte N data
byte N+1 0x17 tail byte (ASCII ETB)
3-6 bc635VME/bc350VXI Time and Frequency Processor (Rev. E) Symmetricom Inc
INTERFACES
Offset 0x28 MASK Reset Value 0xXX00
Table 3-8
Bit # INT # Source Of Interrupt
0
1
2
3
4
5-15
0 External event input has occurred.
1 Periodic pulse output has occurred.
2 Time coincidence strobe has occurred.
3 The one pulse per second (1pps) output has occurred.
4 A data packet is available in the output FIFO.
Reserved
An interrupt source is enabled by writing a one to the mask bit corresponding to that source. An
interrupt source is disabled by writing a zero to the mask bit corresponding to that source.
Offset 0x2A INTSTAT Reset Value 0xXX00
The INTSTAT register has the same basic structure as the MASK register. The TFP sets bits
zero through four of this register depending upon which interrupt source generated the interrupt.
The INTSTAT register bits are set regardless of the state of the mask bits. This feature allows
the host to poll for the occurrence of the interrupt sources. INTSTAT bits are cleared by writing
to the INTSTAT register with the corresponding bit(s) set.
* * * WARNING * * *
It is the transition of an INTSTAT bit from a zero to a one that causes an interrupt to be
generated (assuming that the corresponding MASK bit was set). If the bit in the INTSTAT
register is not cleared by the host it is not possible to generate a second interrupt. It is good
programming practice to clear the INTSTAT register immediately after interrupts have been
enabled.
Offset 0x2C VECTOR Reset Value 0xXX00
The VECTOR register holds the eight bit Status/ID byte that the TFP will return during interrupt
acknowledge cycles for VMEbus applications.
Symmetricom Inc bc635VME/bc350VXI Time and Frequency Processor (Rev. E) 3-7
CHAPTER THREE
Offset 0x2E LEVEL Reset Value 0xXX00
The LEVEL register selects the level at which an interrupt will be generated. Only bits zero
through two are used. These bits are encoded as follows:
Bit IRQ Level
000Disabled
001IRQ1
010IRQ2
011IRQ3
100IRQ4
101IRQ5
110IRQ6
111IRQ7
3-8 bc635VME/bc350VXI Time and Frequency Processor (Rev. E) Symmetricom Inc
CHAPTER FOUR
FIFO DATA PACKETS
4.0 GENERAL
Communication with the TFP is performed using a byte serial data packet protocol. The packet
bytes are read from, and written to the TFP, using D08(O) transfers at offset 0x27 or D16
transfers at offset 0x26. In the case of a D16 transfer, only the low order byte is used. The
packet structure is defined in Chapter Three, “OFFSET 0x26.”
4.1 WRITING DATA PACKETS
The following steps should be followed when loading data packets to the TFP. Failure to
perform one or more of these steps correctly is a common reason for customer support calls.
• Write the packet to the input FIFO.
• Clear bit 0 of the ACK register by writing 0x01 to the ACK register.
• Inform the TFP that an input packet is available by writing 0x80 to the ACK register.
• The TFP will set bit 0 of the ACK register when the packet is processed.
When the host sets bit seven of the ACK register an interrupt to the TFP CPU is generated. The
TFP service routine performs minimalist packet integrity checking. The TFP checks that the
first packet byte is 0x01 (ASCII SOH). If the SOH is found, the TFP loads FIFO data into an
input buffer until a byte value of 0x17 (ASCII ETB) is found. The packet is then processed in
accordance with the idbyte value. When processing is complete, the TFP sets bit zero of the
ACK register, clears the input FIFO, and resumes its previous task. If an SOH is not the first
packet byte, if more than 40 bytes are read before encountering an ETB, or if the idbyte value is
invalid, then TFP clears the FIFO, clears bit zero of the ACK register, and resumes its previous
task.
Symmetricom Inc bc635VME/bc350VXI Time and Frequency Processor (Rev. E) 4-1
CHAPTER FOUR
4.1.1 PACKET “A” SELECT TFP OPERATIONAL MODE
This packet contains a single data byte (zero through seven) which defines the TFP operational
mode. The mode is saved in the battery backed RAM. The modes are enumerated below.
Mode 0 (Zero) Time Code Decoding Mode
The TFP uses an input timecode as the timing reference. See packet “H” for time codes
supported. Both modulated carrier and DC level shift formats are supported (DC level shift is
not supported for 2137 or XR3 codes). The TFP locks its crystal oscillator to the input code rate.
The oscillator has a control range of ±30PPM for the standard DPI version, and ±2PPM for the
optional oven version. If the input code is outside these limits, the TPF will exhibit periodic
slips (if the TFP reference deviates from the input source by more than ± 1 millisecond, a forced
jamsync is performed). If the input code is lost or removed, the TFP will continue to “flywheel”
at the last known code rate. Typical accuracy is five parts in 107 (two milliseconds of drift per
hour).
Mode 1 Free Running Mode
This mode is virtually the same as Mode 2. Without a 1pps input the TFP runs at the last known
oscillator frequency. Major time can be set with the “B” packet. The TFP timebase can be
adjusted with packet “D.”
Mode 2 External 1 pps Mode
The TFP synchronizes to the signal on the 1pps input. Major time can be loaded with the “B”
packet. The acquisition range is the same as described in mode zero.
Mode 3 Real Time Clock Mode
The TFP synchronizes to the onboard real time clock (RTC) IC, and the major time is also
derived from the clock IC. The RTC is battery backed. This mode is not recommended when
using the oven oscillator because the accuracy of the RTC is not high enough to ensure that the
oven will be able to track it with slippages. See Mode 0 (zero) description.
Mode 4 Digital Sync Mode
This mode is not implemented.
Mode 5 GPS Mode with GPS Receiver Onboard (Obsolete)
The TFP only supports this mode in the bc635VME/bc357VXI configuration. It is currently
available only in a double wide 6U form factor.
Mode 6 GPS Mode with GPS Receiver Located in the Antenna
This is an optional mode available with the bc637VME/bc357VXI configuration. It is described
in a separate User's Guide.
4-2 bc635VME/bc350VXI Time and Frequency Processor (Rev. E) Symmetricom Inc
FIFO DATA PACKETS
Mode 7 Diagnostic and Default Setting Mode
Initially this mode was provided to allow the TFP to be photographed. The LED display is
loaded with static time 12:34:56. As more battery backed parameters were added it became
useful to use this mode as a means of setting all battery backed data to standard defaults. This
data and the default values established by mode seven are as follows, see Table 4-1.
Table 4-1
Mode 7 Default Values
Variable Default Description
Mode
Time Code
Format
Gencode
Path
Local
Accum
Leapsec
See Note TFP Operational Mode
IRIG B Reference Time Code Expected
Modulated Modulated Time Code Expected
IRIG B TFP Generates IRIG B
1 Path Selection Variable (See “P” Packet)
0 Local Time Offset (GPS Modes Only)
32000 VCXO DAC Value (Nominally Centered)
0 GPS To UTC Leap Second Correction (Only Used In GPS
Modes)
The diagnostic utility of this mode resides in the fact that the operator can immediately
determine if the host program is communicating properly with the TFP by simply observing the
display. To borrow from the classic K&R, to make 12:34:56 appear “you have to be able to
create the program text, compile it, run it, and find out where your output went. With these
mechanical details mastered, everything else is comparatively easy.”
Note: The bc635 defaults to Mode 0 (zero). The bc637 defaults to Mode 6.
Symmetricom Inc bc635VME/350VXI Time and Frequency Processor (Rev. E) 4-3
CHAPTER FOUR
4.1.2 PACKET “B” SET MAJOR TIME
In Mode 1 and Mode 2 the only way to set major time is using this packet. It is not likely that
this packet would be used in any other mode since all other modes derive major time from the
timing reference signal. The packet format is as follows:
byte 1 SOH
byte 2 “B”
byte 3 days hundreds
byte 4 days tens
byte 5 *days units (Jan 1 is defined as day 001)
byte 6 hours tens
byte 7 hours units
byte 8 minutes tens
byte 9 minutes units
byte 10 seconds tens
byte 11 seconds units
byte 12 ETB
Note: All data fields must be in ASCII format.
*Day 000 is an invalid time code in IRIG time codes. If Day 000 is desired, see “Packet ‘P’ Path
Selection.”
The time loaded by packet “B” will not be used until the one second epoch following the load.
The TFP increments the time before loading it to output buffer registers. The time is
incremented at approximately 918 milliseconds into the current frame, and the buffer registers
are loaded 950 milliseconds into the current frame. The buffer registers are transferred to a set
of holding registers synchronously with the 1pps output. The time loaded by packet “B” should
be input well in advance of the 918 millisecond point in the frame, and should reference the
current frame.
4-4 bc635VME/bc350VXI Time and Frequency Processor (Rev. E) Symmetricom Inc
FIFO DATA PACKETS
4.1.3 PACKET “C” COMMAND INPUT
This packet has a single data byte and is used to direct the TPF to take the specific actions below.
byte 1 SOH
byte 2 “C”
byte 3 “1” - “6” (Definitions Below)
byte 7 ETB
“1” Not Used (Warm Start on Early Software Versions)
“2” Software Reset vectors TFP CPU to Power on Reset Point
“3” Jamsynch Force TFP Minor Time To Zero on the Next 1pps Input
“4” Not Used (Jamsynch Lockout On Early Software Versions)
“5” Buf to RTC Load Current Time to the Real Time Clock IC
“6” Variables Dumps Battery Backed RAM to FIFO (Factory Use Only)
4.1.4 PACKET “D” LOAD D/A CONVERTER
The TFP reference crystal oscillator is voltage controlled using the buffered output of a 16 bit
D/A converter as the controlling voltage. Packet “D” allows the user to directly load a 16 bit
value to the D/A converter. This feature would allow a user to fine tune the TFP time base in the
free running mode. We are not aware of any other use for this packet in normal operation. Since
this voltage is routed out of the TFP via pin 9 on the J1 connector to allow external oscillators to
be disciplined, it would provide a means to devise a frequency control algorithm independent of
the TFP. The format is shown below. (See also bit 3 of the path byte loaded by the “P” packet.)
byte 1 SOH
byte 2 “D”
byte 3 “0” - “F” bits 12-15
byte 4 “0” - “F” bits 08-11
byte 5 “0” - “F” bits 04-07
byte 6 “0” - “F” bits 01-03
byte 7 ETB
Note: All data fields must be in ASCII format.
Symmetricom Inc bc635VME/350VXI Time and Frequency Processor (Rev. E) 4-5
CHAPTER FOUR
4.1.5 PACKET “F” HEARTBEAT (PERIODIC) CONTROL
This packet establishes the frequency of the TFP output periodics. The number of output pulses
is defined by the following equation.
N = 10,000,000 / (n1 * n2)
where N = output pulses per second
n1 = a programmable number in the range of 2 to 65535
n2 = a programmable number in the range of 2 to 65535
The “F” packet establishes the value of n1 and n2. There is a one byte qualifier associated with
the “F” packet. This qualifier allows the periodics to be asynchronous or synchronous with
respect to the 1pps epoch. If the synchronous format is chosen n1 and n2 must be selected such
that N is an integer.
The duty cycle of the output waveform is dependent on the particular values of n1 and n2
selected. Divider n2 physically follows divider n1. The following example serves as an
illustration. If n1 * n2 = 20, the output frequency is 500kHz. If n1 is selected as ten and n2 is
selected as two a square wave is output since the last divider is a divide by two. If n1 is selected
as two and n2 is selected as ten the output waveform is a pulse train with a one tenth duty cycle.
The packet “F” format is as follows:
byte 1 SOH
byte 2 “F”
byte 3 “2” for asynchronous “5” for synchronous
byte 4 “0” - “F” m1 bits 12-15
byte 5 “0” - “F” m1 bits 08-11
byte 6 “0” - “F” m1 bits 04-07
byte 7 “0” - “F” m1 bits 00-03
byte 8 “0” - “F” m2 bits 12-15
byte 9 “0” - “F” m2 bits 08-11
byte 10 “0” - “F” m2 bits 04-07
byte 11 “0” - “F” m2 bits 00-03
byte 12 ETB
If a two (asynchronous) qualifier is used then the values of n1 and n2 are the same as the packet
values m1 and m2. If the five (synchronous) qualifier is used, then the values of n1 and n2 are
equal of packet values m1+1 and m2+1 respectively. For example, if a synchronous 500KHz
square wave is desired then the qualifier byte is five, m1 = 9, and m2 = 1. Additional insight
into the operation of the counter can be gained by reading the Intel documentation for the 82C54
integrated circuit. The two and five qualifiers correspond to the Intel defined Modes 2 and 5.
The periodic engine of the bc635/637VME consists of two sections of an INTEL 82C54
programmable interval timer connected in a serial configuration and driven by the TFP 10 MHz
4-6 bc635VME/bc350VXI Time and Frequency Processor (Rev. E) Symmetricom Inc
FIFO DATA PACKETS
reference. Glue logic in one of the logic cell arrays supports both synchronous (with the 1pps
epoch) and asynchronous operation. It is helpful (although not essential) to read the INTEL data
sheet on the 82C54. Packet "F" allows the user complete access to the serial counters using
standard INTEL loading protocols.
Two counter modes are supported; 1pps synchronous and asynchronous. It is the responsibility
of the user to select the appropriate mode. No error checking is performed by the
bc635/637VME firmware. The synchronous mode should only be selected if the number of
output counts per second is an integer. If the number of counts per second is not an integer then
the asynchronous mode should be used. The number of counts per second is always of the
following form:
N = (10,000,000) / (n1 * n2)
where: N = counts per second
n1 = Counter #1 divide
n2 = Counter #2 divide
The range of values for Counter #1 and #2 is mode dependent as follows.
Asynchronous Mode: 2 to 65535
Synchronous Mode: 3 to 65535
* * * WARNING * * *
Periodic heartbeat pulse/interrupt generation can not be guaranteed in synchronous mode when
counter divide values of two are used.
The two modes of operation are accessed using standard INTEL mode identifiers. For
synchronous operation the mode byte must be an ASCII "5." For asynchronous operation the
mode byte must be an ASCII "2." The packet format is as follows:
byte 1 SOH.
byte 2 "F."
byte 3 ASCII "2" (asynch) or "5" (synch).
byte 4 ASCII "0" - "F" (n1 bits 2-15).
byte 5 ASCII "0" - "F" (n1 bits 8-11).
byte 6 ASCII "0" - "F" (n1 bits 4-7).
byte 7 ASCII "0" - "F" (n1 bits 0-3).
byte 8 ASCII "0" - "F" (n2 bits 12-15).
byte 9 ASCII "0" - "F" (n2 bits 8-11).
byte 10 ASCII "0" - "F" (n2 bits 4-7).
byte 11 ASCII "0" - "F" (n2 bits 0-3).
byte 12 ETB.
Symmetricom Inc bc635VME/350VXI Time and Frequency Processor (Rev. E) 4-7
CHAPTER FOUR
* * * IMPORTANT * * *
When Mode 5 is used, the value of n1 and n2 produced by the 82C54 hardware is n1+1 and
n2+1. This is a result of the way INTEL designed the 82C54, and is unrelated to our design.
Example: It is desired to implement 10000 counts per second synchronous with the 1pps.
mode = "5" (synchronous)
n1+1 = 10
n2+1 = 100 (10,000,000) / (10 * 100) = 10000
byte 1 SOH.
byte 2 "F."
byte 3 "5" (mode).
byte 4 "0."
byte 5 "0."
byte 6 "0."
byte 7 "9" (n1 = 9).
byte 8 "0."
byte 9 "0."
byte 10 "6."
byte 11 "3" (n2 = 99 = 0x63).
byte 12 ETB.
Other values of (n1+1) and (n2+1) could have been used. For example, (n1+1) = 25 and (n2+1) =
40.
4-8 bc635VME/bc350VXI Time and Frequency Processor (Rev. E) Symmetricom Inc
FIFO DATA PACKETS
4.1.6 PACKET “G” PROPOGATION OFFSET CONTROL
It is frequently desired to program an offset into the basic TFP timekeeping functions relative to
the reference input. For example, if the reference input is an IRIG B timecode, there may be
significant cable delay between the IRIG B generator and the TFP location. Packet “G” allows
this time difference to be removed by inserting the known amount of offset between the IRIG B
reference and TFP locations. The offset is programmable in units of one hundred nanoseconds,
and may be positive or negative. The format is shown below.
byte 1 SOH
byte 2 “G”
byte 3 “+” or “-” advance or retard
byte 4 “0” - “9” BCD millisecond hundreds
byte 5 “0” - “9” BCD millisecond tens
byte 6 “0” - “9” BCD millisecond units
byte 7 “0” - “9” BCD microsecond hundreds
byte 8 “0” - “9” BCD microsecond tens
byte 9 “0” - “9” BCD microsecond units
byte 10 “0” - “9” BCD nanosecond hundreds
byte 11 ETB
For the IRIG B scenario described above, a positive offset should be used.
* * * WARNING * * *
If offsets larger than ± 990 microseconds are used, then the TFP jamsynch feature must be turned
off using packet “P.” The reason for this requirement is that under normal operation if a
difference between the reference time and the TFP time is detected to be greater than ±1
millisecond the TFP timbers is “jammed” to the reference time so that a lengthy steering process
is avoided.
Symmetricom Inc bc635VME/350VXI Time and Frequency Processor (Rev. E) 4-9
CHAPTER FOUR
4.1.7 PACKET “H” SET TIMECODE FORMAT FOR MODE 0
Packet “H” allows the host to select the timecode format and modulation type. The packet
format is as follows. The timecode format and modulation values are maintained in battery
backed RAM.
byte 1 SOH
byte 2 “H”
byte 3 format
byte 4 modulation
byte 5 ETB
Format Choices
“A” IRIG A
“B” IRIG B
“C” 2137 (XR3 with 100Hz symbol rate)
“N” NASA 36
“X” XR3 (25Hz symbol rate)
Modulation Choices
“M” amplitude modulated sine wave
Modulated not supported for IRIG A
“D” pulse code modulation (DC level shift)
DC level shift not is supported for 2137 and XR3 codes.
4.1.8 PACKET “I” CLOCK SOURCE SELECT
Packet “I” is used to select the clock source for the TFP. The TFP uses a frequency of 10MHz
for all timing functions. The 10 MHz be may derived from the TFP VCXO or it may be supplied
from an external oscillator via J1 pin #1 or P2 pin #C22. The packet format is as follows.
byte 1 SOH
byte 2 “I”
byte 3 “E” or “I” External or Internal
byte 4 ETB
On power on the TFP always defaults to the internal oscillator selection. This packet has no
effect on boards with Oven Oscillators
4.1.9 PACKET “J” SEND DATA TO GPS RECEIVER
The format and content variations are discussed in a separate User's Guide.
4-10 bc635VME/bc350VXI Time and Frequency Processor (Rev. E) Symmetricom Inc
FIFO DATA PACKETS
4.1.10 PACKET “K” SELECT GENERATOR CODE
The timecode generated by the TFP is selected by packet “K.” Only two options are available as
described below. The generator code type is maintained in battery backed RAM.
byte 1 SOH
byte 2 “K”
byte 3 code
byte 4 ETB
Code Options
“B” generate IRIG B amplitude modulated and DC level shift
“H” generate IRIG H DC level shift only
4.1.11 PACKET “L” SET REAL TIME CLOCK
This packet loads the battery backed real time clock IC which is used as the source of major time
and 1pps epoch when mode three is selected. The format is shown below.
byte 1 SOH
byte 2 “L”
byte 3 years tens
byte 4 years units
byte 5 months tens
byte 6 months units (January = month 1)
byte 7 day-of-month tens
byte 8 day-of-month units
byte 9 hours tens
byte 10 hours units
byte 11 minutes tens
byte 12 minutes units
byte 13 seconds tens
byte 14 seconds units
byte 15 ETB
All data fields must be in ASCII format. The TFP need not be in mode three when packet “L” is
downloaded.
Symmetricom Inc bc635VME/350VXI Time and Frequency Processor (Rev. E) 4-11
CHAPTER FOUR
4.1.12 PACKET “M” LOCAL TIME OFFSET SELECT (GPS MODES ONLY)
This packet allows time to be displayed with a hour offset. This situation usually arises when the
source of time is in an UTC (Universal Time Coordinated) format and the local time is desired to
be displayed. The offset only applies to the hour’s digits. This offset is maintained in battery
backed RAM. The format is as follows.
byte 1 SOH
byte 2 “M”
byte 3 sign “+” or “-”
byte 4 hours tens
byte 5 hours units
byte 6 ETB
The hours are in range, from -12 to +12. A positive sign is used from the prime meridian
heading East, and a negative sign is used from the prime meridian heading West. For example,
Eastern Standard Time would be -05 relative to UTC.
4-12 bc635VME/bc350VXI Time and Frequency Processor (Rev. E) Symmetricom Inc
FIFO DATA PACKETS
4.1.13 PACKET “O” REQUEST DATA FROM THE TFP
This packet is used to request data from the TFP which is not available via the register interfaces.
It was added as a “catch all” packet for universal data transfer. This packet has been created
with a very extensive format, and additional data will be made available as customer needs and
suggestions are addressed. The primary purpose of this packet is to allow the user to verify the
integrity of the programmed setup data.
Note: The user is advised that repetitively issuing Packet “O” can cause excessive CPU
overhead and may disrupt time keeping.
Currently three different data packets may be requested using the “O” packet. The formats are as
follows:
Request Format
byte 1 SOH
byte 2 “O”
byte 3 “0” or “1” or “2” ...
byte 4 ETB
Response Format “0” Request RTC Time (See Packet “L”)
byte 1 SOH
byte 2 “o” (lower case letter)
byte 3 “0” (zero)
byte 4 years tens
byte 5 years units
byte 6 months tens
byte 7 months units
byte 8 day-of-month tens
byte 9 day-of-month units
byte 10 hours tens
byte 11 hours units
byte 12 minutes tens
byte 13 minutes units
byte 14 seconds tens
byte 15 seconds units
byte 16 ETB
Symmetricom Inc bc635VME/350VXI Time and Frequency Processor (Rev. E) 4-13
CHAPTER FOUR
Response Format “1” Request Current D To A Value
byte 1 SOH
byte 2 “o” (lower case letter)
byte 3 “1”
byte 4 “0” - “F” bits 12-15
byte 5 “0” - “F” bits 08-11
byte 6 “0” - “F” bits 04-07
byte 7 “0” - “F” bits 00-03
byte 8 ETB
Response Format “2” Request Leap Seconds (Currently GPS Specific)
byte 1 SOH
byte 2 “o” (lower case letter)
byte 3 “2”
byte 4 leap second tens
byte 5 leap second units
byte 6 ETB
Response Format “3” Request RTC Year
byte 1 SOH
byte 2 “o” (lower case letter)
byte 3 “3”
byte 4 RTC years tens
byte 5 RTC year units
byte 6 ETB
Response Format “4” Request Year
byte 1 SOH
byte 2 “o” (lower case letter)
byte 3 “4”
byte 4 years tens
byte 5 year units
byte 6 ETB
The TFP signals a packet ready condition by setting bit 2 in the ACK register. It is the
responsibility of the host to clear this bit by writing to the ACK register with bit 2 set.
4-14 bc635VME/bc350VXI Time and Frequency Processor (Rev. E) Symmetricom Inc
FIFO DATA PACKETS
4.1.14 PACKET “P” PATH SELECTION
The path selection might better be called a switch or branch selector. The purpose of this packet
is to allow the user to exercise control over certain TFP processes. The path packet is used to
download a single byte. Each bit in the byte has a toggling action relative to a TFP function.
The format is described below.
byte 1 SOH
byte 2 “P”
byte 3 “0” - “F” path upper nibble
byte 4 “0” - “F” path lower nibble
byte 5 ETB
Upper Nibble Bit Definitions
bit 3 0 = normal time format 1 = long second format (See Note.)
bit 2 0 = no broadcast of RTC 1 = broadcast packet “o” “0” each second
bit 1 0 = use GPS leap seconds 1 = ignore GPS leap seconds
bit 0 0 = FIFO echo off 1 = FIFO echo on
Lower Nibble Definitions
bit 3 0 = enable TFP disciplining 1 = disable TFP discipline
bit 2 0 = enable jamsynch 1 = disable jamsynch
bit 1 0 = leap year off 1 = leap year on
bit 0 0 = Accept Day 000 1 = Day 000 invalid (default setting)
Note:Time∅ through TIME4 contain atomic seconds since January 6, 1980. Use only in GPS
Mode. (See Table 4-2.)
4.1.14.1 LOWER NIBBLE BIT DESCRIPTIONS
Bit 0
In Time Code mode (Mode 0) it is sometimes desired to use day 000. This is an invalid code in
IRIG time codes and clearing this bit overrides the normal checking and allows a board lock on
this otherwise invalid code. See Chapter Three for a description of the TIME fields (offset
0x0C).
Note: Day 001 is always January 1 as per IRIG specifications. We allow day 000 only for
those people that want this capability, say for testing purposes (many time-code
generators start with Day 000), and are not bothered by an extra day in the year roll over.
Symmetricom Inc bc635VME/350VXI Time and Frequency Processor (Rev. E) 4-15
CHAPTER FOUR
Bit 1
During leap years this path bit must be set to enable the different day counts which represent
leap years.
Note: Software versions later than 9501128 use the “S” packet to set the year and then
calculates the leap year. In this software the leap year bit has no effect.
Bit 2
Jamsynch is a method employed to match the output 1pps signal to the input time mark. If you
change modes of operation on a warmed up unit and want to rush the re-synchronizing you can
enable jamsynch, then use Packet “C” to force a jamsynch of the unit, which will cause the 1pps
signal to be reset to the time-mark time. There are disadvantages to using this method. If a
strobe was scheduled for a time between the flywheeling time and the jamsynch it will be missed
in the jump to the new time. There is also a break in the lock for a couple of seconds.
Jamsynchs are ineffective on a cold unit that has the oscillator changing frequency at a high rate
during warm up.
Bit 3
Oscillator disciplining might be disabled if you were using an external clock source that requires
a different disciplining routine and you are using the on-board DAC and disciplining through a
Packet “D.”
4.1.14.2 UPPER NIBBLE BIT DESCRIPTIONS
Bit 0
When enabled, packets written to the INPUT FIFO will be automatically echoed to the OUTPUT
FIFO.
Bit 1
This bit is used when you want to report UTC time instead of GPS time. The change is that leap
seconds are added to the time to derive UTC.
Bit 2
When enabled, the RTC data is automatically inserted into the OUT-FIFO every second. This
could be useful if you have a system that is maintaining two different times such as UTC and
local time.
Bit 3
In GPS mode (Mode 5 or 6) you may want to report the time in seconds from the start of the
GPS epoch (seconds from start of January 6, 1980). Some systems may find it easier to deal
with time strictly in seconds. The table below reflects that fields TIME1 and TIME2 contain a
32 bit contiguous binary number representing GPS Epoch seconds. The minor time remains in
decimal sub-seconds as reflected by Table 4-2.
4-16 bc635VME/bc350VXI Time and Frequency Processor (Rev. E) Symmetricom Inc
FIFO DATA PACKETS
Table 4-2
Time1 and Time2 Fields
Bit # 15-12 11-8 7-4 3-0
TIME0 Field
TIME1 Field
TIME2 Field
TIME3 Field
TIME4 Field
Not Defined. Not Defined. Status. Unused.
228 Seconds. 224 Seconds. 220 Seconds. 216 Seconds.
212 Seconds. 28 Seconds. 24 Seconds. Seconds.
10E-1 Seconds. 10E-2 Seconds. 10E-3 Seconds. 10E-4 Seconds.
10E-5 Seconds. 10E-6 Seconds. 10E-7 Seconds. Not Defined.
4.1.15 PACKET “Q” SET DISCIPLINING GAIN
This packet allows the gain and sense of the disciplining process to be set via the host bus.
Originally this feature was used for Symmetricom developmental purposes, but it would also be
indispensable to anyone attempting to discipline an external oscillator using the TFP. The
format is as follows.
byte 1 SOH
byte 2 “Q”
byte 3 “0” - “F” least significant nibble
byte 4 “0” - “F” most significant nibble
byte 5 sense: “1” = positive, “0” = negative
byte 6 ETB
4.1.16 PACKET “S” SET YEAR
This packet allows users to set the year in Modes 0, 1, and 2. This is necessary to get the leap
year calculator to function in these modes. After writing the year you must wait at least one full
second before reading it back using the “O” packet.
byte 1 SOH
byte 2 “S”
byte 3 years tens
byte 4 years units
byte 5 ETB
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CHAPTER FOUR
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4-18 bc635VME/bc350VXI Time and Frequency Processor (Rev. E) Symmetricom Inc
CHAPTER FIVE
PROGRAMMING EXAMPLES
5.0 GENERAL
The example code fragments in this chapter are written in the C programming language. The
examples have been tested at Symmetricom, and should be transportable to most programming
environments. A system dependent base address is defined below where “YYYY” indicates a 64
kbyte page of memory used for A16 data and “SSSS” indicates the SW1 and SW2 switch
settings.
#define BASE 0xYYYYSSSS
The following definitions pertain to FIFO data transfer.
#define SOH 0x01
#define ETB 0x17
#define FIFO (short*)(BASE+0x27)
The following global variables are also declared and used throughout this chapter.
short dummy, *readptr, time[5] ;
long i ;
5.1 READING TIME ON DEMAND
The following example reads the time from the TFP registers TIME0 through TIME4 and loads
this data into the array time[ ]. The time is latched by reading the TIMEREQ register, and the
register is assigned to a global variable. In most cases assignment to a global avoids the
possibility that the dummy read operation will be removed by an optimizing compiler (beware).
readptr = (short*)(BASE + 0x0A) ; /* initialize pointer */
dummy = *readptr++ ; /* latch time increment pointer */
for(i=0 ; i<5 ; i++) time[i] = *readptr++ ; /* read the time registers */
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CHAPTER FIVE
5.2 EXTERNAL EVENT TIME CAPTURE
This example sets up the TFP event capture to occur on a rising edge and generate an interrupt.
The time capture lockout mechanism is also used.
#define EVENT0 (short*)(BASE+0x16)
#define CMD (short*)(BASE+0x24)
#define VECTOR (short*)(BASE+0x2C)
#define MASK (short*) (BASE+0x28)
#define INTSTAT (short*)(BASE+0x2A)
#define LEVEL (short*)(BASE+0X2E)
#define UNLOCK (short*)(BASE+0x20
/* INITIALIZE TFP EVENT HARDWARE */
*CMD = 0x09 ; /* enable event and lockout */
*VECTOR = 0x40 ; /* interrupt vector */
*LEVEL = 0x03 ; /* interrupt level set */
*INSTAT = 0x01 ; /* clear INSTAT bit */
*MASK = 0x01 ; /* enable the interrupt */
/* INTERRUPT SERVICE ROUTINE FRAGMENT */
readptr = EVENT0 ;
for(i=0 ; i<5 ; i++) time[i] = *readptr++;
dummy = *UNLOCK ; /* release capture lockout */
*INTSTAT = 0x01 ; /* clear INSTAT bit */
5-2 bc635VME/bc350VXI Time and Frequency Processor (Rev. E) Symmetricom Inc
PROGRAMMING EXAMPLES
5.3 PROGRAM PERIODIC FREQUENCY OF 1,000 HZ
This example uses a generalized send_packet( ) function to program a 1,000 Hz output periodic
synchronized to the TFP 1pps epoch.
#define ACK (short*)(BASE+0x22)
void send_packet(char *charptr)
{
*FIFO = SOH ;
while(*charptr) *FIFO = *charptr++ ; /* load body of packet */
*FIFO = ETB ;
*ACK = 0x81 ; /* command TFP & clear ACK */
while(!(*ACK & 0x01)) ; /* wait for TFP acknowledge */
}
/* CODE FRAGMENT WHICH SETS PERIODIC */
send_packet("F500630063") ; /* 0x0063 = 99 = (100-1) */
5.4 SET MODE 1 AND THE MAJOR TIME
This example selects the free running mode and sets the TFP major time, using the “B” packet.
send_packet("A1") ; /* select mode 1 */
*INSTAT = 0x08 ; /* clear INSTAT 1pps bit */
while(!(*INSTAT & 0x08) ; /* wait for 1pps */
send_packet("B123112233") ; /* set the days through seconds */
5.5 SELECT MODE 0 (IRIGB) AND ADVANCE TFP 2.5 MILLISECONDS
The following code fragment selects the mode, timecode, and offset. The last “P" packet is used
to disable jamsynchs since the required offset is larger than 990 microseconds. See the “G”
packet description for additional details on the jamsynch function.
send_packet("A0") ; /* select mode 0 */
send_packet("HB") ; /* select IRIGB timecode */
send_packet("G+0025000") ; /* advance 2.5 milliseconds */
send_packet("P04") ; /* disable jamsynchs */
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5-4 bc635VME/bc350VXI Time and Frequency Processor (Rev. E) Symmetricom Inc
CHAPTER SIX
INPUTS AND OUTPUTS
6.0 INPUTS AND OUTPUTS
The front panel I/O for the bc635VME and the bc350VXI (B-size) consists of an LED time and
status display, a BNC timecode input, a BNC timecode output, a 15 pin “D” plug, and a 15 pin
“D” socket.
The current TFP time hr:min:sec is displayed using seven segment LED digits. If the TFP is
flywheeling, the digit decimal points are also illuminated. The time display is incremented at
990 milliseconds into the current frame. (One customer measured the LED radix point with a
photo diode and reported that it was indeed early!)
Timecode is input using BNC connector J3 or J1-7. Input amplitudes from 0.5 to 5 volts peak to
peak are accommodated. Timecode is output on BNC connector J2 or J1-5. The output
amplitude is adjustable using ten turn potentiometer VR1 located just below J2 and accessible
with the TFP in place. The signals on socket J1 and plug J4 are summarized in Table 6-1 on the
following page.
Symmetricom Inc bc635VME/bc350VXI Time and Frequency Processor (Rev. E) 6-1
CHAPTER SIX
Pin Signal Pin Signal
1 *External 10MHz Input or
2 Ground 2 RS-422 Rx(-)
3 Strobe Output 3 RS-422 Tx(+)
4 1 PPS Output 4 RS-422 Tx(-)
5 Time Code Output (AM) 5 Ground
6 External Event Input 6 Not Used
7 Time Code Input 7 GPS 1PPS
8 Time Code Return 8 GPS RS-422 1PPS+
9 Oscillator Control Output 9 GPS RS-422 1PPS10 Not Used 10 Ground
11 Time Code Output (DCLS) 11 GPS RS-422 Tx(-)
12 Ground 12 GPS RS-422 Tx(+)
13 1,5,10 MHz Output 13 Not Used
14 External 1PPS Input 14 Ground
15 Periodics Output 15 GPS +12 VDC
Table 6-1
Socket J1 and Plug 4 Signals
Signals On J1 15 Pin “DS” Signals On J4 15 Pin “DP”
1 RS-422 Rx(+)
Ovenized Oscillator Output
* Pin 1 is an output when the optional ovenized oscillator is installed.
6-2 bc635VME/bc350VXI Time and Frequency Processor (Rev. E) Symmetricom Inc
Table 6-2
TFP Signals on the P2 Connector
TFP Signals On VMEbus P2
Pin Signal
C1 Time Code Input
C2 Time Code Return
C3 Time Code Output (DCLS)
C4 Time Code Output (AM)
C6 External Event Input
C8 Strobe Output
C9 Periodic Output
C10 External 1PPS Input
C11 1PPS Output
C12 1,5,10MHz Output (Note 2)
C22 10MHz Input
C24 Oscillator Control Output
C18 C20 RS-422 Tx(+) Rx(+)
A18 A20 RS-422 Tx(-) Rx(-)
A26 RS-422 Rx(-) GPS (Note 1)
C26 RS-422 Rx(+) GPS (Note 1)
A28 GPS 1PPS (Note 1)
INPUTS AND OUTPUTS
Note: Hardware Rev. E and later.
Note 2: Hardware Rev. G and later See JP6.
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6-4 bc635VME/bc350VXI Time and Frequency Processor (Rev. E) Symmetricom Inc
CHAPTER SEVEN
ADJUSTMENTS
7.0 GENERAL
There are only two adjustments on the TFP module, VR1 and VR2. (See figure 1-1 for the
location of these potentiometers.)
7.1 TIME CODE PHASE LOCK LOOP ADJUSTMENT
VR2 adjusts the center frequency of the VCO, which locks to the carrier of a modulated input
time code. This adjustment is made at the factory and rarely needs adjustment by the customer.
This adjustment can be verified and adjusted correctly using a dual trace oscilloscope and a time
code input.
• Set the TFP to Mode 0 (Packet “A”) and select the appropriate time code format and
modulation type (Packet “H”).
• Connect channel #1 of the oscilloscope to pin #16 of U19 (XR2212). Connect channel #2 of
the oscilloscope to the modulated input time code. Trigger the oscilloscope on the channel
#1 input.
• Adjust VR2 so that the positive transition of the TTL signal input to channel #1 is centered
on the positive crest of the input sine wave. The negative TTL transition should be centered
on the most negative part of the input sine wave. See Figure 7-1 below.
Figure 7-1
Phase Lock Loop Adjustment
Symmetricom Inc bc635VME/bc35VXI Time and Frequency Processor (Rev. E) 7-1
CHAPTER SEVEN
7.2 TIME CODE OUTPUT AMPLITUDE ADJUSTMENT
VR1 adjusts the amplitude of the modulated IRIG B output time code. A value of one volt RMS
is common as is three volts peak-to-peak on the high cycles. Adjust this value to suit the
equipment being driven. The range is zero to twenty-four volts peak-to-peak.
7-2 bc635VME/bc35VXI Time and Frequency Processor (Rev. E) Symmetricom Inc
SYMMETRICOM TIMING TEST & MEASUREMENT
3750 Westwind Blvd.
Santa Rosa, California
95403 USA
tel : 707-528-1230
fax : 707-527-6640
info
@symmetricom.com
www.symmetricom.com
For more information about the complete range of Quality Timing Products from the
Symmetricom Group of Companies, call 1-800-544-0233 in the US and Canada.
Or visit our site on the world wide web at http://www.symmetricom.com
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