Yaesu FT-817ND Operating Manual page 73

CAT S
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 DATA BYTE FORMAT
There are 17 instruction opcodes for the FT-817
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. Irre-
spective 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" Eargument 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-817
ACC 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

43
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/off" is 02. Placing the opcode
into the 5th data bit position, we then enter dummy values into all other parameter
locations:
DATA 1

00
FT-817 Operating Manual
ND
YSTEM
CPU via the computer's serial port and the transceiver's
ND
DATA 2 DATA 3
97 00
Parameter
DATA 2 DATA 3
00 00
Dummy Data
P
ROGRAMMING
    
CAT 5-BYTE COMMAND STRUCTURE
, listed in the chart on next page. Many
ND
DATA 4
00
DATA 4
00
DATA 5
01
Command
DATA 5
02
Command
71