User`s guide

with success, so it is possible to single-step through a program or proceed from a PAUSE
instruction without loss of data.
Input Processing
Input data is received by V+ according to the byte format specified by the I/O configuration
program. The size of the buffer can be set with the CONFIG_C utility program. Data errors
such as parity or framing errors are also buffered and are returned in the proper order.
The possible data errors from the serial input lines are:
-522 *Data error on device*
A data byte was received with incorrect parity, or the byte generated a
framing error.
-524 *Communications overrun*
Data bytes were received after the input buffer was full, or faster than V+
could process them.
-526 *No data received*
If data is expected, continue polling the serial line.
-504 *Unexpected end of file*
A BREAK was received from the remote device.
Serial line input data is normally read using the GETC function, since it allows the most
flexible response to communications errors. The READ instruction also can be used provided
that input data is terminated by a Line-Feed character (10 decimal).
V+ does not support input echoing or input line editing for the serial lines.
Output Processing
All serial line output is performed using the WRITE instruction. All binary data (including NULL
characters) is output without conversion. If the serial line is configured to support parity, a
parity bit is automatically appended to each data byte.
By default, the WRITE instruction appends a Return character (13 decimal) and a Line-Feed
character (10 decimal) to each data record unless the /S format control is specified in the
instruction parameter list.
If output flow control is enabled and output has been suspended by a Ctrl+S character from
the remote device, a WRITE request may wait indefinitely before completing.
Serial Line I/O
V+Language User's Guide, v17.0
Page 224