Manual

5-2 RS-232C Communications
Outputs to the Host
When the Automove System sends data back to the host it also uses 7-bit ASCII.
Transmitted parity is the same as the received parity established by the backpanel switches.
The Automove System always transmits two stop bits, although it is happy to receive either
one or two.
Many host computers have only one or two characters of buffering on their RS-232C input
channel. This means that, if the host software does not read and process the characters as
fast as the Automove System sends them, data will be lost. If your host software is losing
characters you can ask the Automove System to delay and slow down its transmissions. See
the turnaround delay in the.
ESC M command and the intercharacter delay in the ESC.N
command, Chapter 6.
When an ACL command or escape sequence requests status information the Automove
System sends one or more numeric values to the host. Multiple values are separated by
commas. A negative number is preceded by a minus sign. Following the last value, the
System sends the Output Terminator sequence. At power up this sequence defaults to a
Carriage Return (ASCII code 13) followed by a Linefeed (ASCII code 10); it can be changed
via the
ESC.M command. See Chapter 6.
In general, when the host requests output data (via either an ACL command or an escape
sequence), it should await the response before sending any more characters (including
handshake characters) to the Automove System. This is not an absolute rule but, if followed,
may prevent host/Automove handshake deadlocks and unpredictable sequences of status
information change.
It is a good idea for the host program always to read the data into a string variable instead of
directly into a numeric variable. That way if an Exceptional Condition (see below) occurs or
has occurred, the "?" will be the first character of the string, and the host program can simply
check the string before trying to decode the numbers themselves. (Some BASIC interpreters,
for example, don't like getting a question mark when they are expecting a number.)