Serial Ports - GE VersaMax PLC User Manual

2.4 Serial Ports

34 GFK-1503E
For public disclosure
The two serial ports are software-configurable for SNP slave or RTU master or slave
operation. 4-wire and 2-wire RTU are supported. If a port is being used for RTU, it
automatically switches to SNP slave mode if necessary. Both ports default to SNP slave
and both automatically revert to SNP slave when the CPU is in Stop mode, if configured
for Serial I/O. Either port can be software-configured to set up communications between
the CPU and various serial devices. An external device can obtain power from Port 2 if it
requires 100mA or less at 5VDC.
Port 1: is an RS-232 port with a 9-pin female D-sub connector. The
pinout of Port 1 allows a simple straight-through cable to connect with a
standard AT-style RS-232 port. Maximum cable lengths from the CPU
to the last device attached to the cable are:
Baud Rate
19.2 K and below
38.4K
57.6K
115.2K
Port 2: is an RS-485 port with a 15-pin female D-sub connector. This
can be attached directly to an RS-485 to RS-232 adapter
(IC690ACC901). Maximum cable lengthsfrom the CPU to the last
device attached to the cable is Port 2 1200 meters (4000 ft.)
The following table compares the functions of Port 1 and Port 2.
CPU Protocols (SNP slave,
RTU master/slave, Serial I/O)
Firmware Upgrade
Smart module firmware
upgrade
Maximum Cable Length
15 meters (50 ft.)
7.5 meters (25 ft.)
5 meters (16 ft.)
2.5 meters (8 ft.)
Port 1
Defaults to SNP slave
PLC in Stop/No I/O mode
PLC in Stop/No I/O mode
VersaMax PLC User Manual
Port 2
Defaults to SNP slave
No
PLC in Stop/No IO mode