Set Up Input Buffer Function (4301) - Emerson PaCSystems VersaMax Series User Manual

User Manual
GFK-1503F
Example Command Block for the Initialize Port Function
address
address +1
address +2
address +3
address +4
address +5
address +6
Operating Notes
Note:
CAUTION
If this COMMREQ is sent when a Write Bytes (4401) COMMREQ is transmitting a string from
a serial port, transmission is halted. The position within the string where the transmission is
halted is indeterminate. In addition, the final character received by the device the CPU is
sending to is also indeterminate.
12.4.5

Set Up Input Buffer Function (4301)

This function can be used to change the size of the internal memory buffer where input data
will be placed as it is received. By default, the buffer is set to a maximum of 2K bytes. As data
is received from the serial port it is placed in the input buffer. If the buffer becomes full, any
additional data received from the serial port is discarded and the Overflow Error bit in the
Port Status word (See Read Port Status Function) is set.
Retrieving Data from the Buffer
Data can be retrieved from the buffer using the Read String or Read Bytes function. It is not
directly accessible from the application program.
If data is not retrieved from the buffer in a timely fashion, some characters may be lost.
Serial I/O / SNP / RTU Protocols
VALUE VALUE
(decimal) (hexadecimal)
0001 0001
0000 0000
0008 0008
0000 0000
0000 0000
0000 0000
4300 10CC
COMMREQs that are cancelled due to this command executing do not have their
respective COMMREQ status words updated.
MEANING
Data block length
NOWAIT mode
Status word memory type (%R)
Status word address minus 1 (%R0001)
Not used
Not used
Initialize port command
Chapter 12
Jan 2020
214