Reference Manual

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PMAC 2 Software Reference

306 PMAC Program Command Specification

for a new command, program execution is temporarily halted until the new command can

be placed on the queue.

Also, commands that generate a response to the host (including errors if I6 is not equal to

2) potentially can fill up the response queue if there is no host or the host is not prepared

to read the responses. This will temporarily halt program execution until the response

queue is emptied. In standalone applications, it is a good idea to set I1 to 1, disabling the

serial handshake, so any responses can be sent out the serial port (the default response

port) at any time, even if there is no host to receive it.

In a PLC program, it is a good idea to have at least one of the conditions that caused the

command issuance to occur set false immediately. This will prevent the same command

from being issued again on succeeding scans of the PLC, overflowing the command

and/or response queues.

Typically in a motion program, the time between moves prevents this overflow unless

there are a lot of commands and the moves take a very short time.

PMAC will not issue an acknowledging character (<ACK> or <LF>) to a valid command

issued from a program. It will issue a <BELL> character for an invalid command issued

from a program unless I6 is set to 2. It is a good idea to have I6 not set to 2 in early

development so you will know when PMAC has rejected such a command. Setting I6 to

2 in the actual application can prevent program hang up from a full response queue, or

from disturbing the normal host communications protocol.

If PMAC variable I64 is set to 1, any response sent to the host as a result of an internal

COMMAND statement is preceded by a <CTRL-B> character, making it easier for the host

computer to tell that this is an unsolicited response.

Many otherwise valid commands will be rejected when issued from a motion program.

For instance, you cannot jog any motor in the coordinate system executing the program,

because all these motors are considered to be running in the program, even if the program

is not requesting a move of the motors at that time.

When issuing commands from a program, be sure to include all the necessary syntax

(motor and/or coordinate system specifiers) in the command statement or use the

ADDRESS command. For example, use CMD"#4HM" and CMD"&1A" instead of

CMD"HM" and CMD"A". Otherwise, motor and coordinate system commands will be

sent to the most recently addressed motor and coordinate system.

Example

COMMAND"#1J+"

CMD"#4HM"

CMD"&1B5R"

CMD"P1"

47.5

ADDRESS#3

COMMAND"J-"

IF(M40=1 AND M41=1)

CMD"&4R"

M41=0

ENDIF