Specifications

114 FT-857D Operating Manual
CAT Data Protocol
All commands sent from the computer to the transceiver consist of five-byte blocks, with
up to 200 ms between each byte. The last byte in each block is the instruction opcode, while
the first four bytes of each block are arguments (either parameters for that instruction, or
dummy values required to pad the block out to five bytes). Each byte consists of 1 start bit,
8 data bits, no parity bit, and two stop bits.
CAT OPERATION
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CAT DATA BYTE FORMAT
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CAT 5-BYTE COMMAND STRUCTURE
There are 17 instruction opcodes for the FT-857D, listed in the chart on next page. Many of
these opcodes are On/Off toggle commands for the same action (e.g. “PTT On” and “PTT
Off”) Most of these commands require some parameter or parameters to be set. Irrespective
of the number of parameters present, every Command Block sent must consist of five bytes.
Accordingly, any CAT control program must construct the five-byte block by selecting the
appropriate instruction opcode, organizing the parameters as needed, and providing unused
“dummy” argument bytes to pad the block to its required five-byte length (the dummy
bytes can contain any value). The resulting five bytes are then sent, opcode last, from the
computer to the FT-857D CPU via the computer’s serial port and the transceiver’s CAT/
LINEAR jack.
All CAT data values are hexadecimal
Constructing and Sending CAT Commands
Example #1: Set the VFO frequency to 439.70 MHz
Per the CAT command table, the opcode for “Set Frequency” is 01. Placing the opcode into
the 5th data bit position, we then enter the frequency into the first four data bit positions:
DATA 1 DATA 2 DATA 3 DATA 4 DATA 5
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43 97 00 00 01
Parameter Command
Send these five bytes to the transceiver, in the order shown above.
Example #2: Turn the Split Mode “On”
Per the CAT command table, the opcode for “Split On” is 02. Placing the opcode into the
5th data bit position, we then enter dummy values into all other parameter locations:
DATA 1 DATA 2 DATA 3 DATA 4 DATA 5
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00 00 00 00 02
Dummy Data Command
L.S.D
Parame ter
1
Parameter
2
Parameter
3
Parame ter
4
M.S.D.
Command