GE PACSystems RX7i - Overlapping Commreqs

Chapter 6. Serial I/O, SNP & RTU Protocols
GFK-2222AD April 2018 211
6.2.5 Overlapping COMMREQs
Some Serial I/O COMMREQs must complete execution before another COMMREQ can be processed.
Others can be left pending while others are executed.
COMMREQS that Must Complete Execution
■ Autodial (4400)
■ Initialize Port (4300)
■ Set Up Input Buffer (4301)
■ Flush Input buffer (4302)
■ Read port status (4303)
■ Write port control (4304)
■ Cancel Operation (4399)
■ Serial Port Setup (FFF0)
COMMREQs that can be Pending While Others Execute
The table below shows whether Write Bytes, Read Bytes and Read String COMMREQs can be pending
when other COMMREQs are executed.
NEW COMMREQ
Currently-Pending
COMMREQs
Autodial
(4400)
Write
Bytes
(4401)
Initialize Port
(4300)
Set Up Input
Buffer (4301)
Flush Input
Buffer
(4302)
Read
Port
Status
(4303)
Write
Port
Control
(4304
)
Read
Bytes
(4402)
Read String
(4403)
Cancel
Operation
(4399)
Serial Port
Setup (FFF0)
Write Bytes
(4401)
No
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
Read Bytes
(4402)
No
Yes
Yes
No
No
Yes
Yes
No
No
Yes
No
Read String
(4403)
No
Yes
Yes
No
No
Yes
Yes
No
No
Yes
No