The SCN2652/68652 Multi-Protocol Communications Controller
(MPCC) is a monolithic n-channel MOS LSI circuit that formats,
transmits and receives synchronous serial data while supporting
bit-oriented or byte control protocols. The chip is TTL compatible,
operates from a single +5V supply, and can interface to a processor
with an 8 or 16-bit bidirectional data bus.
– 8 or 16-bit tri-state data bus
– Error control – CRC or VRC or none
– Character length – 1 to 8 bits for BOP or 5 to 8 bits for BCP
– SYNC or secondary station address comparison for BCP-BOP
– Idle transmission of SYNC/FLAG or MARK for BCP-BOP
•Automatic detection and generation of special BOP control
sequences, i.e., FLAG, ABORT, GA
•Zero insertion and deletion for BOP
•Short character detection for last BOP data character
•SYNC generation, detection, and stripping for BCP
•Maintenance mode for self-testing
•TTL compatible
•Single +5V supply
INDEX
CORNER
NOTE: DB00 is least significant bit, highest number
(that is, DB15, A2) is most significant bit.
Operating ambient temperature
Storage temperature–65 to +150°C
All inputs with respect to GND
1
PARAMETERRATINGUNIT
2
3
Note 4°C
–0.3 to +7V
NOTES:
1. Stresses above those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating only
and functional operation of the device at these or at any other condition above those indicated in the operation sections of this specification
is not implied.
2. For operating at elevated temperatures the device must be derated based on +150
°
C maximum junction temperature.
3. This product includes circuitry specifically designed for the protection of its internal devices from the damaging effects of excessive static
charge. Nonetheless, it is suggested that conventional precautions be taken to avoid applying any voltages larger than the rated maxima.
4. Parameters are valid over operating temperature range unless otherwise specified. See ordering code table for applicable temperature
range and operating supply range.
BYTE22I
CE1IChip Enable: A high input permits a data bus operation when DBEN is activated.
R/W18I
DBEN23I
RESET33IReset: A high level initializes all internal registers (to zero) and timing.
MM40I
RxE8I
RxA5O
RxDA*6O
RxC2I
S/F4OSYNC/FLAG: S/F is asserted for one RxC clock time when a SYNC or FLAG character is detected.
RxSA*7O
RxSI3IReceiver Serial Input: RxSI is the received serial data. Mark = ‘1’, space = ‘0’.
TxE37I
TxA34O
TxBE*35O
TxU*36O
TxC39I
TxSO38OTransmitter Serial Output: TxSO is the transmitted serial data. Mark = ‘1’, space = ‘0’.
V
CC
GND9IGround: 0V reference ground.
*Indicates possible interrupt signal
17–10
24–31
32I+5V: Power supply.
Data Bus: DB07–DB00 contain bidirectional data while DB15–DB08 contain control and status
information to or from the processor. Corresponding bits of the high and low order bytes can be wire
I/O
OR’ed onto an 8-bit bus. The data bus is floating if either CE or DBEN are low.
Address Bus: A2–A0 select internal registers. The four 16-bit registers can be addressed on a word or
byte basis. See Register Address section.
Byte: Single byte (8-bit) data bus transfers are specified when this input is high. A low level specifies
16-bit data bus transfers.
Read/Write: R/W controls the direction of data bus transfer . When high, the data is to be loaded into the
addressed register. A low input causes the contents of the addressed register to be presented on the
data bus.
Data Bus Enable: After A2–A0, CE, BYTE and R/W are set up, DBEN may be strobed. During a read,
the 3-state data bus (DB) is enabled with information for the processor. During a write, the stable data is
loaded into the addressed register and TxBE will be reset if TDSR was addressed.
Maintenance Mode: MM internally gates TxSO back to RxSI and TxC to RxC for off line diagnostic
purposes. The RxC and RxSI inputs are disabled and TxSO is high when MM is asserted.
Receiver Enable: A high level input permits the processing of RxSI data. A low level disables the
receiver logic and initializes all receiver registers and timing.
Receiver Active: RxA is asserted when the first data character of a message is ready for the processor.
In the BOP mode this character is the address. The received address must match the secondary station
address if the MPCC is a secondary station. In BCP mode, if strip-SYNC (PCSAR13) is set, the first
non-SYNC character is the first data character; if strip-SYNC is zero, the character following the second
SYNC is the first data character. In the BOP mode, the closing FLAG resets RxA. In the BCP mode, RxA
is reset by a low level at RxE.
Receiver Data Available: RxDA is asserted when an assembled character is in RDSRL and is ready to
be presented to the processor. This output is reset when RDSRL is read.
Receiver Clock: RxC (1X) provides timing for the receiver logic. The positive going edge shifts serial
data into the RxSR from RxSI.
Receiver Status Available: RxSA is asserted when there is a zero to one transition of any bit in RDSR
except for RSOM. It is cleared when RDSRH is read.
Transmitter Enable: A high level input enables the transmitter data path between TDSRL and TxSO. At
the end of a message, a low level input causes TxSO = 1(mark) and TxA = 0 after the closing FLAG
(BOP) or last character (BCP) is output on TxSO.
Transmitter Active: TxA is asserted after TSOM (TDSR8) is set and TxE is raised. This output will reset
when TxE is low and the closing FLAG (BOP) or last character (BCP) has been output on TxSO.
Transmitter Buffer Empty: TxBE is asserted when theTDSR is ready to be loaded with new control
information or data. The processor should respond by loading theTDSR which resets TxBE.
Transmitter Underrun: TxU is asserted during a transmit sequence when the service of TxBE has been
delayed for one character time. This indicates the processor is not keeping up with the transmitter. Line
fill depends on PCSAR
falling edge of TxC.
Transmitter Clock: TxC (1X) provides timing for the transmitter logic. The positive going edge shifts
data out of the TxSR to TxSO.
. TxU is reset by RESET or setting of TSOM (TDSR8), synchronized by the
11
H
1995 May 01
4
Page 5
Philips SemiconductorsProduct specification
These registers are used for character assembly (CSSR
PCRParameter control register8RDSRH contains receiver status information.
RDSRReceive data/status register16RDSRL = RxDB contains the received assembled character.
*H = High byte – bits 15–8
L = Low byte – bits 7–0
Table 2.Error Control
CHARACTERDESCRIPTION
FCSFrame check sequence is transmitted/received
BCCBlock check character is transmitted/received as
as 16 bits following the last data character of a
BOP message. The divisor is usually
CRC–CCITT (X
16
+ X12 + X5 + 1) with dividend
preset to 1’s but can be other wise determined
by ECM. The inverted remainder is transmitter as
the FCS.
two successive characters following the last data
character of a BCP message. The polynomial is
CRC–16 (X
16
+ X15 + X2 + 1) or CRC–CCITT
with dividend preset to 0’s (as specified by
ECM). The true remainder is transmitted as the
BCC.
PCSARH and PCR contain parameters common to the
receiver and transmitter. PCSARL contains a programmable
SYNC character (BCP) or secondary station address (BOP).
TDSRH contains transmitter command and status
information. TDSRL = TxDB contains the character to be
transmitted
HSR, RxSR), disassembly (TxSR), and CRC
accumulation/generation (RxCRC, TxCRC).
Table 3.Special Characters
OPERATIONBIT PATTERNFUNCTION
BOP
FLAG01111110Frame message
ABORT11111111 generation Terminate communication
01111111 detection
GA01111111
Address(PCSARL)
1
BCP
SYNC
(PCSARL) or
2
(TxDB)
generation
NOTES:
1. ( ) = contents of.
2. For IDLE = 0 or 1 respectively.
Terminate loop mode
repeater function
Secondary station address
Character synchronization
,
APAPCSAR
PCR
RDSR
TDSR
NOTE:
Refer to Register Formats for mnemonics and description.
The MPCC can be functionally partitioned into receiver logic,
transmitter logic, registers that can be read or loaded by the
processor, and data bus control circuitry. The register bit formats are
shown in Figure 3 while the receiver and transmitter data paths are
depicted in Figures 4 and 3.
RECEIVER OPERATION
General
After initializing the parameter control registers (PCSAR and PCR),
the RxE input must be set high to enable the receiver data path. The
serial data on the RxSI is synchronized and shifted into an 8-bit
Control Character Shift Register (CCSR) on the rising edge of RxC.
A comparison between CCSR contents and the FLAG (BOP) or
SYNC (BCP) character is made until a match is found. At that time,
the S/F output is asserted for one RxC time and the 16-bit Holding
Shift Register (HSR) is enabled. The receiver then operates as
described below.
BOP Operation
A flowchart of receiver operation in BOP mode appears in Figure 6.
Zero deletion (after five ones are received) is implemented on the
received serial data so that a data character will not be interpreted
as a FLAG, ABORT, or GA. Bits following the FLAG are shifted
through the CCSR, HSR, and into the Receiver Shift Register
(RxSR). A character will be assembled in the RxSR and transferred
to the RDSR
RxDA output will be asserted and the processor must take the
character no later than one RxC time after the next character is
assembled in the RxSR. If not, an overrun (RDSR11 = 1) will occur
and succeeding characters will be lost.
The first character following the FLAG is the secondary station
address. If the MPCC is a secondary station (PCSAR
contents of RxSR are compared with the address stored in
PCSAR
for the station; the RxA output is asserted, the character is loaded
into RDSR
(RSOM) is set. No match indicates that another station is being
addressed and the receiver searches for the next FLAG.
If the MPCC is a primary station, (PCSAR
address check is made; RxA is asserted and RSOM is set once the
first non-FLAG character has been loaded into RDSR
has been asserted. Extended address field can be supported by
software if PCSAR
When the 8 bits following the address character have been loaded
into RDSR
The processor should read this 8-bit character and interpret it as the
Control field.
Received serial data that follows is read and interpreted as the
information field by the processor. It will be assembled into character
lengths as specified by PCR
time a character has been transferred into RDSR
when RDSR
when RxSA is asserted. This occurs on a zero to one transition of
any bit in RDSR
except RSOM are cleared when RDSRH is read. The processor
for presentation to the processor. At that time the
L
= 1), the
12
. A match indicates the forthcoming message is intended
L
, RxDA is asserted and the Receive Start of Message bit
L
= 0), no secondary
12
and RxDA
L
= 0.
12
and RxDA has been asserted, RSOM will be cleared.
L
. As before, RxDA is asserted each
8–10
is read by the processor. RDSRH should only be read
L
except for RSOM. RxSA and all bits in RDSR
H
and is cleared
L
H
should check RDSR
set, then RDSR
12–15
each time RxSA is asserted. If RDSR9 is
9–15
should be examined.
Receiver character length may be changed dynamically in response
to RxDA: read the character in RxDB and write the new character
length into RxCL. The character length will be changed on the next
receiver character boundary . A received residual (short) character
will be transferred into RxDB after the previous character in RxDB
has been read, i.e. there will not be an overrun. In general the last
two characters are protected from overrun.
The CRC–CCITT, if specified by PCSAR
, is accumulated in
8–10
RxCRC on each character following the FLAG. When the closing
FLAG is detected in the CCSR, the received CRC is in the 16-bit
HSR. At that time, the Receive End of Message bit (REOM) will be
set; RxSA and RxDA will be asserted. The processor should read
the last data character in RDSR
RDSR
. If RDSR15 = 1, there has been a transmission error; the
9–15
accumulated CRC–CCITT is incorrect. If RDSR
and the receiver status in
L
≠ 0, last data
12–14
character is not of prescribed length. Neither the received CRC nor
closing FLAG are presented to the processor. The processor may
drop RxE or leave it active at the end of the received message.
RxBCP Operation
The operation of the receiver in BCP mode is shown in Figure 7.
The receiver initially searches for two successive SYNC characters,
of length specified by PCR
The next non-SYNC character or next SYNC character, if stripping is
not specified (PCSAR
13
enables the receiver data path. Once enabled, all characters are
assembled in RxSR and loaded into RDSR
character is available in RDSR
transition of any bit in RDSR
or RDSR
are read respectively.
H
If CRC–16 error control is specified by PCSAR
must determine the last character received prior to the CRC field.
When that character is loaded into RDSR
the received CRC will be in CCSR and HSR
transmission error, the processor must read the receiver status
(RDSR
) and examine RDSR15. This bit will be set for one
H
character time if an error free message has been received. If
RDSR
= 0, the CRC–16 is in error. The state of RDSR15 in BCP
15
CRC mode does not set RxSA. Note that this bit should be
examined only at the end of a message. The accumulated CRC will
include all characters starting with the first non-SYNC character if
PCSAR
PCSAR
= 1, or the character after the opening two SYNCs if
13
= 0. This necessitates external CRC generation/checking
13
when supporting IBM’s
BISYNC. This can be accomplished using the Philips
Semiconductors SCN2653 Polynomial Generator/Checker. See
Typical Applications.
If VRC has been selected for error control, parity (odd or even) is
regenerated on each character and checked when the parity bit is
received. A discrepancy causes RDSR
asserted. This must be sensed by the processor. The received parity
bit is stripped before the character is presented to the processor.
When the processor has read the last character of the message, it
should drop RxE which disables the receiver logic and initializes all
receiver registers and timing.
After the parameter control registers (PCSAR and PCR) have been
initialized, TxSO is held at mark until TSOM (TDSR
is raised. Then, transmitter operation depends on protocol mode.
1995 May 01
) is set and TxE
8
?
YES
FLAG
?
YES – END OF MESSAGE
NO
NO
TxBOP Operation
Transmitter operation for BOP is shown in Figure 8. A FLAG is sent
after the processor sets the Transmit Start of Message bit (TSOM)
and raises TxE. The FLAG is used to synchronize the message that
follows. TxA will also be asserted. When TxBE is asserted by the
MPCC, the processor should load TDSR
the message. TSOM should be cleared at the same time TDSR
with the first character of
L
is
L
loaded (16-bit data bus) or immediately thereafter (8-bit data bus).
FLAGS are sent as long as TSOM = 1. For counting the number of
FLAGs, the processor should reassert TSOM in response to the
assertion of TxBE.All succeeding characters are loaded into TDSR
by the processor when TxBE = 1. Each
character is serialized in TxSR and transmitted on TxSO. Internal
zero insertion logic stuffs a “0” into the serial bit stream after five
successive “1s” are sent. This insures a data character will not
match a FLAG, ABORT, or GA reserved control character. As each
character is transmitted, the Frame Check Sequence (FCS) is
generated as specified by Error Control Mode (PCSAR
FCS should be the CRC–CCITT polynomial (X
16
+ X12 + X5 + 1)
8–10
). The
preset to 1s. If an underrun occurs (processor is not keeping up with
the transmitter), TxU and TERR (TDSR
) will be asserted with
15
ABORT or FLAG used as the TxSO line fill depending on the state
of IDLE (PCSAR
). The processor must set TSOM to reset the
11
underrun condition. To retransmit the message, the processor
should proceed with the normal start of message sequence.
A residual character of 1 to 7 bits may be transmitted at the end of
the information field. In response to TxBE, write the residual
character length into TxCL and load TxDB with the residual
character. Dynamic alteration of character length should be done in
exactly the same sequence. The character length will be changed
on the next transmit character boundary.
After the last data character has been loaded into TDSR
to TxSR (TxBE = 1), the processor should set TEOM (TDSR
and sent
L
). The
9
MPCC will finish transmitting the last character followed by the FCS
and the closing FLAG. The processor should clear TEOM and drop
TxE when the next TxBE is asserted. This corresponds to the start
of closing FLAG transmission. When TxE has been dropped. TxA
will be low 1 1/2 bit times after the last bit of the closing FLAG has
been transmitted. TxSO will be marked after the closing FLAG has
been transmitted.
If TxE and TEOM are high, the transmitter continues to send
FLAGs. The processor may initiate the next message by resetting
TEOM and setting TSOM, or by loading TDSR
with a data
L
character and then simply resetting TSOM (without setting TSOM).
TxBCP Operation
Transmitter operation for BCP mode is shown in Figure 9. TxA will
be asserted after TSOM = 1 and TxE is raised. At that time SYNC
characters are sent from PCSAR
as TSOM = 1. TxBE is asserted at the start of transmission of the
first SYNC character. For counting the number of SYNCs, the
processor should reassert TSOM in response to the assertion of
TxBE. When TSOM = 0 transmission is from TDSR
loaded with characters from the processor each time TxBE is
asserted. If this loading is delayed for more than one character time,
an underrun results: TxU and TERR are asserted and the
TxSO line fill depend on IDLE (PCSAR
TSOM and retransmit the message to recover. This is not
compatible with IBM’s BISYNC, so that the user must not underrun
when supporting that protocol.
or TDSRL (IDLE = 0 or 1) as long
L
, which must be
L
). The processor must set
11
CRC–16, if specified by PCSAR
character transmitted from TDSR
, is generated on each
8–10
when TSOM =0. The processor
L
must set TEOM = 1 after the last data character has been sent to
TxSR (TxBE = 1). The MPCC will finish transmitting the last data
character and the CRC–16 field before sending SYNC characters
L
which are transmitted as long as TEOM = 1. If SYNCs are not
desired after CRC–16 transmission, the processor should clear
TEOM and lower TxE when the TxBE corresponding to the start of
CRC–16 transmission is asserted. When TEOM = 0, the line is
marked and a new message may be initiated by setting TSOM and
raising TxE.
If VRC is specified, it is generated on each data character and the
data character length must not exceed 7 bits. For software LRC or
CRC, TEOM should be set only if SYNC’s are required at the end of
the message block.
SPECIAL CASE: The capability to transmit 16 spaces is provided
for line turnaround in half duplex mode or for a control recovery
situation. This is achieved by setting TSOM and TEOM, clearing
TEOM when TxBE = 1, and proceeding as required.
PROGRAMMING
Prior to initiating data transmission or reception, PCSAR and PCR
must be loaded with control information from the processor. The
contents of these registers (see Register Format section) will
configure the MPCC for the user’s specific data communication
environment. These registers should be loaded during power-on
initialization and after a reset operation. They can be changed at any
time that the respective transmitter or receiver is disabled.
The default value for all registers is zero. This corresponds to BOP,
primary station mode, 8-bit character length, FCS = CRC–CCITT
preset to 1s.
For BOP mode the character length register (PCR) may be set to
the desired values during system initialization. The address and
control fields will automatically be 8-bits. If a residual character is to
be transmitted, TxCL should be changed to the residual character
length prior to transmission of that character.
DATA BUS CONTROL
The processor must set up the MPCC register address (A2–A0),
chip enable (CE), byte select (BYTE), and read/write (R
before each data bus transfer operation.
During a read operation (R
/W = 0), the leading edge of DBEN will
initiate an MPCC read cycle. The addressed register will place its
contents on the data bus. If BYTE = 1, the 8-bit byte is placed on
DB15–08 or DB07–00 depending on the H/L status of the register
addressed. Unused bits in RDSR
are zero. If BYTE = 0, all 16 bits
L
(DB15–00) contain MPCC information. The trailing edge of DBEN
will reset RxDA and/or RxSA if RDSR
or RDSRH is addressed
L
respectively.
DBEN acts as the enable and strobe so that the MPCC will not
begin its internal read cycle until DBEN is asserted.
During a write operation (R
and/or DB
prior to the leading edge of DBEN. The stable data
07–00
/W = 1), data must be stable on DB
is strobed into the addressed register by DBEN. TxBE will be
cleared if the addressed register was TDSR
Table 6. Parameter Control SYNC/Address Register (PCSAR)–(R/W)
BITNAMEMODEFUNCTION
00–07S/ARBOPSYNC/address register. Contains the secondary station address if the MPCC is a secondary
BCPSYNC character is loaded into this register by the processor. It is used for receive and
08–10ECMBOP/BCPError Control Mode1098 Suggested Mode Char. length
11IDLEDetermines line fill character to be used if transmitter underrun occurs (TxU asserted and
BOPIDLE = 0, transmit ABORT characters during underrun and when TABORT = 1.
BCPIDLE = 0 transmit initial SYNC characters and underrun line fill characters from theS/AR.
12SAMBOPSecondary Address Mode = 1 if the MPCC is a secondary station. This facilitates automatic
13SS/GAStrip SYNC/Go Ahead. Operation depends on mode.
BOPSS/GA = 1 is used for loop mode only and enables GA detection. When a GA is detected as a
BCPSS/GA = 1, causes the receiver to strip SYNC’s immediately following the first two SYNC’s
14PROTODetermines MPCC Protocol mode
BOPPROTO = 0
BCPPROTO = 1
15APABOPAll parties address. If this bit is set, the receiver data path is enabled by an address field of
station. The contents of this register is compared with the first received non-FLAG character
to determine if the message is meant for this station.
transmit bit synchronization with bit length specified by RxCL and TxCL.
CRC–CCITT preset to 1’s 000BOP1–8
CRC–CCITT preset to 0’s 001BCP8
Not used010–––
CRC–16 preset to 0’s011BCP8
VRC odd100BCP5–7
VRC even101BCP5–7
Not used110–––
No error control111BCP/BOP5–8
ECM should be loaded by the processor during initialization or when both data paths are idle.
TERR set) and transmission of special characters for BOP/BCP.
IDLE = 1, transmit FLAG characters during underrun and when TABOR T = 1.
IDLE = 1 transmit initial SYNC characters from TxDB and marks TxSO during underrun.
recognition of the received secondary station address. When transmitting, the processor must
load the secondary address into TxDB.
SAM = 0 inhibits the received secondary address comparison which serves to activate the
receiver after the first non-FLAG character has been received.
closing character, REOM and RAB/GA will be set and the processor should terminate the
repeater function. SS/GA = 0 is the normal mode which enables ABORT detection. It causes
the receiver to terminate the frame upon detection of an ABORT or FLAG.
detected. SYNC’s in the middle of a message will not be stripped. SS/GA = 0, presents any
SYNC’s after the initial two SYNC’s to the processor.
‘11111111’ as well as the normal secondary station address.
00–07TxDBBOP/BCPTransmit data buffer. Contains processor loaded characters to be serialized in TxSR and
08TSOMTransmitter start of message. Set by the processor to initiate message transmission provided
BOPTSOM = 1 generates FLAGs. When TSOM = 0 transmission is from TxDB and FCS
BCPTSOM = 1 generates SYNCs from PCSARL or transmits from TxDB for IDLE = 0 or 1
09TEOMTransmit end of message. Used to terminate a transmitted message.
BOPTEOM = 1 causes the FCS and the closing FLAG to be transmitted following the transmission
BCPTEOM = 1 causes CRC–16 to be transmitted (if selected) followed by SYNCs from PCSAR
10TABORTBOPTransmitter abort = 1 will cause ABORT or FLAG to be sent (IDLE = 1 or 1) after the current
11TGABOPTransmit go ahead (GA) instead of FLAG when TEOM = 1. This facilitates repeater
12–14Not Defined
15TERRRead
only
BOPABORT’s or FLAG’s are sent as fill characters (IDLE = 0 or 1)
BCPSYNC’s or MARK’s are sent as fill characters (IDLE = 0 or 1). For IDLE = 1 the last character
transmitted on TxSO.
TxE = 1.
generation (if specified) begins. FCS, as specified by PCSAR
preset to 1’s.
respectively. When TSOM = 0 transmission is from TxDB and CRC generation (if specified)
begins.
of the data character in TxSR. FLAGs are transmitted until TEOM = 0. ABORT or GA are
transmitted if T ABORT or TGA are set when TEOM = 1.
or TxDB (IDLE = 0 or 1). Clearing TEOM prior to the end of CRC–16 transmission (when
TxBE = 1) causes TxSO to be marked following the CRC–16. TxE must be dropped before a
new message can be initiated. If CRC is not selected, TEOM should not be set.
character is transmitted. (ABORT = 11111111)
termination in loop mode. (GA = 01111111)
Transmitter error = 1 indicates the TxDB has not been loaded in time (one character time–1/2
TxC period after TxBE is asserted) to maintain continuous transmission. TxU will be asserted
to inform the processor of this condition. TERR is cleared by setting TSOM. See timing
diagram.
00–07RxDBBOP/BCPReceiver data buffer. Contains assembled characters from the RxSR. If VRC is specified, the
08RSOMBOPReceiver start of message = 1 when a FLAG followed by a non-FLAG has been received and
09REOMBOPReceiver end of message = 1 when the closing FLAG is detected and the last data character
10RAB/GABOPReceived ABORT or GA character = 1 when the receiver senses an ABORT character if
11RORBOP/BCPReceiver overrun = 1 indicates the processor has not read last character in the RxDB within
12–14ABCBOPAssembled bit count. Specifies the number of bits in the last received data character of a
15RERRBOP/BCPReceiver error indicator should be examined by the processor when REOm = 1 in BOP, or
parity bit is stripped.
the latter character matches the secondary station if SAM = 1. RxA will be asserted when
RSOM = 1. RSOM resets itself after one character time and has no affect on RxSA.
is loaded into RxDB or when an ABORT/GA character is received. REOM is cleared on
reading RDSRH, reset operation, or dropping of RxE.
SS/GA = 0 or a GA character if SS/GA = 1. RAB/GA is cleared on reading RDSRH, reset
operation, or dropping of RxE. A received abort does not set RxDA.
one character time + 1/2 RxC period after RxDA is asserted. Subsequent characters will be
lost. ROR is cleared on reading RDSRH, reset operation, or dropping of RxE.
message and should be examined by the processor when REOM = 1(RxDA and RxSA
asserted). ABC = 0 indicates the message was terminated (by a flag or GA) on a character
boundary as specified by PCR
character. ABC is cleared when RDSR
residual character is right justified inRDSRL.
. Otherwise, ABC = number of bits in the last data
8–10
is read, reset operation, or dropping RxE. The
H
when the processor determines the last data character of the message in BCP with CRC or
when RxSA is set in BCP with VRC.
CRC–CCITT preset to 1’s/0’s as specified by PCSAR
RERR = 1 indicates FCS error (CRC ≠ F0B8 or ≠ 0)
8–10
:
RERR = 0 indicates FCS received correctly (CRC = F0B8 or = 0)
CRC–16 preset to 0’s on 8-bit characters specified by PSCAR
RERR = 1 indicates CRC–16 received correctly (CRC = 0).
Address/control set-up50
Address/control hold0
Data bus set-up (write)50ns
Data bus hold (write)0
Receiver serial data set-up150
Receiver serial data hold150
Pulse width
t
RES
t
DBEN
RESET250ns
DBEN250m
4
Delay Time
t
DD
t
TxD
t
DBEND
t
DF
Data bus (read)170
Transmit serial data250
DBEN to DBEN delay200
Data bus float time (read)150ns
fClock (RxC, TxC) frequency2.0MHz
t
CLK1
t
CLK2
t
CLK0
Clock high (MM = 0)165
Clock high (MM = 1)240ns
Clock low240
NOTES:
1. Parameters are valid over operating temperature range unless otherwise specified. See ordering code table for applicable temperature
range and operating supply range.
2. All voltage measurements are referenced to ground. All time measurements are at 0.8V or 2.0V. Input voltage levels for testing are 0.4V and
1. SYNC may be 5 to 8 bits and will contain parity bit as specified.
2. TxA goes high relative to TxC rising edge after TSOM has been set and TxE has been raised.
3. TxBE goes low relative to DBEN falling edge on the first write transfer into TDSR. It is reasserted 1 TxC time before the first bit of the transmitted SYNC/FLAG. TxBE then goes
low relative to DBEN falling edge when writing into TDSR
character, except in BOP mode when the CRC is to be sent as the next character (see Transmit Timing–End of Message).
3
SET TSOMLOAD 1st CHAR RESET TSOMLOAD 2nd CHAR
2
and/or TDSRL. It is reasserted on the rising edge of the TxC that corresponds to the transmission of the last bit of each
1. TxBE goes low relative to the falling edge of DBEN corresponding to loading TDSR
dropped.
2. TxE can be dropped before resetting TEOM if TxBE (corresponding to the closing FLAG) is high. Alternatively TxE can remain high and a new message initiated.
3. TxA goes low after TxE has been dropped and 1 1/2 TxC’s after the last bit of the closing FLAG has been transmitted.
. It goes high one TxC before character transmission begins and also when TxA has been
H/L
FLAGCRCLAST CHARNEXT TO LAST CHAR
MARK
Figure 13. Timing Diagrams (cont.)
TRANSMIT TIMING – END OF BCP MESSAGE
TxC
SD00068
LAST CHARNEXT TO LAST CHAR
TxBE
LOAD LAST CHARSET TEOMRESET TEOM
DBEN
TxE
TxA
NOTE:
1. When SCN2652 generated CRC is not required. TEOM should only be set if SYNCs are to follow the message block. In that case, TxE should be dropped in response to TxBE
(which corresponds to the start of transmission of the last character). When CRC is required, TxE must be dropped before CRC transmission is complete. Otherwise, the contents
of TxDB will be shifted out on TxSO. This facilitates transmission of contiguous messages.
1. TxU goes active relative to TxC falling edge if TxBE has not been serviced after n-1/2 TxC times (where n = transmit character length). TxU is reset on the TxC falling edge following assertion of the TSOM command.
2. An underrun will occur at the next character boundary if TEOM is reset and the transmitter remains enabled, unless the TSOM command is asserted or a character is loaded into
the TxDB.
SD00070
Figure 15. Timing Diagrams (cont.)
RECEIVE – START OF MESSAGE
RxC
RxA
1st CHAR READY
TO BE READ
2
RxDA
DBEN
3
S/F
RxE
NOTES:
1. RxA goes high relative to falling edge of RxC when RxE is high and: a. A data character following two SYNC’s is in RxDB (BCP mode). b. Character following FLAG is in RxDB
(BOP primary station mode). c. Character following FLAG is in RxDB and character matches the secondary station address or all parties address (BOP secondary station mode).
2. RxDA goes high on RxC falling edge when a character in RxDB is ready to be read. It comes up before RxSA and goes low on the falling edge of DBEN when RxDB is read.
3. S/F goes high relative to rising edge of RxC anytime a SYNC (BCP) or FLAG (BOP) is detected.
1. At the end of a BOP message, RxSA goes high when FLAG detection (S/F 1) forces REOm to be set. Processor should read the last data character (RDSRL) and status (RDSRH)
which resets RxDA and RxSA respectively. For BCP end of message, RxSA may not be set and S/F = 0. The processor should read the last data character and status.
2. RxE must be dropped for BCP with non-contiguous messages. It may be left on at the end of a BOP message (see BOP Receive Operation).
3. RxA is reset relative to the falling edge of RxC after the closing FLAG of a BOP message (REOM = 1 and RxSA active.) or when RxE is dropped.
DATA
READ
STATUS
SD00072
Figure 17. Timing Diagrams (cont.)
TYPICAL APPLICATIONS
SCN2652 MPCC MICROPROCESSOR INTERFACE
RESET
RESET
CLOCK
TS BUFFER
DATA BUS
8-BIT
µP
Φ
ADDRESS CONTROL
A2–A0, R/W DBEN CE
“1”
STATUS
DB0–DB7
BYTE
MPCC
SCN2652
TxC
RxC
TxSO
RxSI
LR
LR
SYNCHRO-
NOUS
LD
LR
MODEM
RxETxE
MODEM
CONTROL
LOGIC
NOTES:
1. Possible µP interrupt requests are: RxDA RxSA TxBE TxU
2. Other SCN2652 status signals and possible uses are S F line idle indicator, frame delimiter. RxA handshake on RxE, line turn around control. TxA handshake on TxE, line turn
around control.
3. Line drivers/receivers (LD/LR) convert EIA to TTL voltages and vice-versa.
4. RTS should be dropped after the CRC (BCP) or FLAG (BOP) has been transmitted. This forces CTS low and TxE low.
5. Corresponding high and low order bits of DB must be OR tied.
This data sheet contains the design target or goal specifications for product development.
Specification may change in any manner without notice.
This data sheet contains preliminary data, and supplementary data will be published at a later date.
Philips Semiconductors reserves the right to make chages at any time without notice in order to
improve design and supply the best possible product.
This data sheet contains final specifications. Philips Semiconductors reserves the right to make
changes at any time without notice in order to improve design and supply the best possible product.
[1]
[1] Please consult the most recently issued datasheet before initiating or completing a design.
Definitions
Short-form specification — The data in a short-form specification is extracted from a full data sheet with the same type number and title. For
detailed information see the relevant data sheet or data handbook.
Limiting values definition — Limiting values given are in accordance with the Absolute Maximum Rating System (IEC 134). Stress above one
or more of the limiting values may cause permanent damage to the device. These are stress ratings only and operation of the device at these or
at any other conditions above those given in the Characteristics sections of the specification is not implied. Exposure to limiting values for extended
periods may affect device reliability.
Application information — Applications that are described herein for any of these products are for illustrative purposes only. Philips
Semiconductors make no representation or warranty that such applications will be suitable for the specified use without further testing or
modification.
Disclaimers
Life support — These products are not designed for use in life support appliances, devices or systems where malfunction of these products can
reasonably be expected to result in personal injury . Philips Semiconductors customers using or selling these products for use in such applications
do so at their own risk and agree to fully indemnify Philips Semiconductors for any damages resulting from such application.
Right to make changes — Philips Semiconductors reserves the right to make changes, without notice, in the products, including circuits, standard
cells, and/or software, described or contained herein in order to improve design and/or performance. Philips Semiconductors assumes no
responsibility or liability for the use of any of these products, conveys no license or title under any patent, copyright, or mask work right to these
products, and makes no representations or warranties that these products are free from patent, copyright, or mask work right infringement, unless
otherwise specified.
Philips Semiconductors
811 East Arques Avenue
P.O. Box 3409
Sunnyvale, California 94088–3409
Telephone 800-234-7381
Copyright Philips Electronics North America Corporation 1998
All rights reserved. Printed in U.S.A.
print codeDate of release: 08-98
Document order number:
1998 May 01
28
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