Serial I/O Commreq Commands; Overlapping Commreqs - GE VersaMax PLC User Manual

12.4 Serial I/O COMMREQ Commands

236 GFK-1503E
For public disclosure
The following COMMREQs are used to implement Serial I/O:
• Local COMMREQs - do not receive or transmit data through the serial port.
− Initialize Port (4300)
− Set Up Input Buffer (4301)
− Flush Input Buffer (4302)
− Read Port Status (4303)
− Write Port Control (4304)
− Cancel Operation (4399)
• Remote COMMREQs - receive and/or transmit data through the serial port.
− Autodial (4400)
− Write bytes (4401)
− Read bytes (4402)
− Read String (4403)

12.4.1 Overlapping COMMREQs

Some of the Serial I/O COMMREQs must complete execution before another
COMMREQ can be processed. Others can be left pending while others are executed.
12.4.2
• 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)
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