Sub-Audio Signaling Processor
Page 11 of 24
MX805A
5.2 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
(ii) a Status or data Reply
Instructions and data are loaded and transferred, via C-BUS, in accordance with the timing information in
Figure 9 and Figure 11.
Placing the Address Select input at a logic “0” will address MX805A #1, a logic “1” will address MX805A #2.
Table 4 and Table 5 show the list of A/C bytes relevant to the MX805A
Command Assignment
Address/Command (A/C) byte
Data Bytes
Hex
Binary
MSB
LSB
General Reset
Write to Control Register
01
70
00000001
01110000
+1 byte instruction to Control
Register
Read Status Register
Read CTCSS Rx Freq. Reg.
71
72
73
01110001
01110010
01110011
+1 byte reply from Status Register
+2 byte reply of CTCSS Rx Data
Write to CTCSS Tx Freq./NRZ
+2 byte instruction for Tx Frequency
Baud Rate Reg.
and NRZ Tx/Rx baud rates
Read NRZ Rx Data Reg.
Write to NRZ Tx Data Reg.
Write to Gain Set Reg.
74
75
76
01110100
01110101
01110110
+1 byte binary data Reply
+1 byte binary data Command
+1 byte instruction for Tx Output
Table 4: MX805A #1 C-BUS Address/Commands – (Address Select input at a logic “0”)
Command Assignment
Address/Command (A/C) byte
Data Bytes
Hex
Binary
MSB
LSB
General Reset
Write to Control Register
01
78
00000001
01111000
+1 byte instruction to Control
Register
Read Status Register
Read CTCSS Rx Freq. Reg.
79
7A
7B
01111001
01111010
01111011
+1 byte reply from Status Register
+2 byte reply of CTCSS Rx Data
Write to CTCSS Tx Freq./NRZ
+2 byte instruction for Tx Frequency
Baud Rate Reg.
and NRZ Tx/Rx baud rates
Read NRZ Rx Data Reg.
Write to NRZ Tx Data Reg.
Write to Gain Set Reg.
7C
7D
7E
01111100
01111101
01111110
+1 byte binary data Reply
+1 byte binary data Command
+1 byte instruction for Tx Output
Table 5: MX805A #2 C-BUS Address/Commands – (Address Select input at a logic “1”)
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