Read Port Status Function (4303) - GE PACSystems RX7i Reference Manual

6.2.9 Read Port Status Function (4303)

This function returns the current status of the port. The following events can be detected:
1. A read request was initiated previously and the required number of characters has now been
received or the specified time-out has elapsed.
2. A write request was initiated previously and transmission of the specified number of characters is
complete or a time-out has elapsed.
The status returned by the function indicates the event or events that have completed. More than one
condition can occur simultaneously, if both a read and a write were initiated previously.
Example Command Block for the Read Port Status Function
VALUE
(decimal)
Address 0003
Address +1 0000
Address +2 0008
Address +3 0000
Address +4 0000
Address +5 0000
Address +6 4303
Address +7 0076
Address +8 0101
Port Status
The port status consists of a status word and the number of characters in the input buffer that have not
been retrieved by the application (characters which have been received and are available).
word 1 Port status word (see below)
word 2 Characters available in the input buffer
GFK-2222AD
VALUE MEANING
(hexadecimal)
0003 Data block length
0000 NOWAIT mode
0008 Status word memory type (%R)
0000 Status word address minus 1 (%R0001)
0000 Not used
0000 Not used
10CF Read port status command
004C Port status memory type (%M)
0065 Port status memory offset (%M101)
April 2018
Chapter 6. Serial I/O, SNP & RTU Protocols
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