INFICON SRT-422 Crucible Indexer - Manual (Page 55)

RS-232 Interface Page 53
Section 4.5: Communication Commands
A set of commands follow which when used allow control of and communications with
the Source Indexer by a process controller or a PC type computer. These commands follow
the ASCII protocol described above. The function of each command along with its form and a
typical response is described below. Note: In a response, the first byte after the ‘$’ is the
response byte which encodes the success or failure of the command and the status of the
reset flag. See the paragraph following the command set for a complete explanation of the
response byte.
Section 4.6: Command Responses
In response to all messages received with a valid protocol, the first byte returned after
the ‘$’ is the response byte which may be one of the following.
Reset Flag Cleared Reset Flag Set
Message OK ‘*’ ‘#’
Illegal Command ‘3’ ‘4’
Illegal Data Value ‘5’ ‘6’
Illegal Syntax ‘7’ ‘8’
All commands received with a valid protocol (‘$’ first char and last char) will return
some type of response based on the message received and the state of the Reset Flag. The
Reset Flag is set when power is first applied to the unit. The Flag remains set until it is cleared
by the RS-232 command R. The purpose of the Reset flag is to notify a remote control source
that the SRT has been turned off and back on again or a power failure has occurred so it may
take the appropriate steps if necessary. A typical control program would initially clear the
Reset flag, then test the response byte of each response to see if some type of power failure
has occurred.
For example, assume you have written a program to talk to the Indexer through the
serial port. Your program is running and you set the current pocket to Three (3). After the
pocket is set you have a power failure of short duration and the SRT is reset. Next you may
issue a command and you notice the response byte indicates you had a power failure. This
may be a problem for the following reason. Your program assumes you have set the current
pocket of 3, but on a power fail reset the unit to pocket 1. An appropriate action at this point
may be to set the correct pocket.
Response to a valid Set Parameter command. A response to a successful set
command with the reset flag cleared would be $* where $ and are the protocol, *
says the message was received and there has been no power failures since the Reset flag
was cleared.
Response to a valid Ask Parameter command
A response to a successful ask command with the reset flag set would be $#1.5 where #
indicates there has been a power failure (if you reset the flag when your program started) the
1.5 indicates the value of the parameter you requested.