5
Controlling Protocol
Control of the FX803 Audio Signalling Processor's operation is by communication between the µController and the FX803
internal registers on the “C-BUS,” using Address/Commands (A/Cs) and appended instructions or data (see Figure 7). The use
and content of these instructions is detailed in the following paragraphs and tables.
Address/Commands
The first byte of a loaded data sequence is always
recognized by the “C-BUS” as an Address/Command (A/C)
byte. Instruction and data transactions to and from this
device consist of an Address/Command byte followed by
either:
(i) further instructions or data or,
(ii) a Status or data Reply.
Instructions and data are loaded and transferred, via
“C-BUS,” in accordance with the timing information given in
Figures 7 and 8.
Table 1 shows the list of A/C bytes relevant to the FX803.
A complete list of DBS 800 “C-BUS” Address allocations is
published in the System Support Document.
(Rx) HIGH BAND
Frequency (Hz)
(Tx) TONE GENERATORS 1 and 2
(Rx) EXTENDED BAND
(Rx) HIGH BAND
0 1000 2000 3000 4000 5000 6000
208Hz to 3000Hz
1250Hz to 6000Hz
625Hz to 3000Hz
313Hz to 1500Hz
(Rx) MID BAND
0 1000 2000 3000 4000 5000 6000
Frequency (Hz)
FX803 Internal Registers
FX803 internal registers are detailed below:
Control Register (30
H
) – Write Only, control and
configuration of the FX803.
Status Register (31
H
) – Read Only, reporting of device
functions.
Rx Tone Frequency Register (32H) – Read Only, indicates
frequency of the last received input.
Rx N
OTONE Timer Register (33
H
) – Write Only, setting of the
Rx N
OTONE period.
Tx Tone Generator 1 Register (34
H
) – Write Only, setting
the required output frequency from Tx Tone Generator 1.
Tx Tone Generator 2 Register (35H) – Write Only, setting
required output frequency from Tx Tone Generator 2.
General Purpose Timer Register (36
H
) – Write Only,
setting of a general purpose, sequential time period.
Command Address/Command (A/C) Byte + Data
Assignment Hex. Binary Byte/s
MSB LSB
General Reset 01 0 0 0 00001
Write to Control Register 30 0 0 1 10000 + 1 byte Instruction to Control Register
Read Status Register 31 0 0 1 10001 + 1 byte Reply from Status Register
Read Rx Tone Frequency 32 0 0 1 10010 + 2 byte Reply from Rx Tone Register
Write to N
OTONE Timer 33 0 0 1 10011 + 1 byte Instruction to NOTONE Register
Write to Tx Tone Gen. 1 34 0 0 1 10100 + 2 byte Instruction to Tx Tone Gen. 1
Write to Tx Tone Gen. 2 35 0 0 1 10101 + 2 byte Instruction to Tx Tone Gen. 2
Write to G/Purpose Timer 36 0 0 1 10110 + 1 byte Instruction to G/Purpose Timer
Table 1 “C-BUS” Address/Commands
Fig.4 FX803 Frequencies