APPENDIX D: COMMUNICATIONS
CD-A DUAL PULSE RESISTANCE WELDING POWER SUPPLY
D-2
990-430
Section II. Communications Protocol and Commands
Command Format
Each external command will be formatted as follows:
<stx> <cmd> <cnt> <data> <cksum> <etx>.
Definition of a Command:
<stx>
1 byte
The data packet will start with a STX (start of text 0x02) character.
<cmd>
2 bytes
This is a two character ASCII string denoting the command. (i.e. “TY”)
<cnt>
2 bytes
This is a count of data bytes to follow, converted into a decimal ASCII
number. (“00” to “99”)
<data>
n
bytes
This is ASCII numbers or ASCII data and may or may not be required
by the command. See the individual command.
Multiple byte ordering is: [MSB][…][LSB]
<cksum>
2 bytes
This is a two charter ASCII HEX string calculated from the sum of all
bytes except <stx>, <cksum>, and <etx>. Then masked with 255 (0xFF)
<etx>
1 byte
This terminates the transmission. (End of text 0x03)
The CD-A will respond with a Negative Acknowledge Command (“
NK
”)
when an error is encountered
in response to a command. The format and reasons follow.
<stx>
“NK”
<cnt> <err> <cksum> <etx>
Where <err> = ‘1’
‘2’
‘3’
NO<SOH>
BAD checksum
Unrecognized command
‘4’
‘5’
‘6’
Timeout
In Local
Data Bad
A valid command will return EITHER DATA OR
“AK”
.
The
<ACK>
format is:
<stx> “AK” <cnt> <data> <cksum> <etx>
The
DATA
format is:
<stx> <cmd> <cnt> <ascii data> <cksum> <etx>
When you issue a command to the CD-A, you need to wait for the response before you issue the next
command. This waiting period should be at least 250ms. The CD-A should respond within this timeout.
VARIABLE:
italics.
RANGE OF PARAMETERS:
low_end - high_end
(separated by hyphen).
