Serial Ports - GE VersaMax PLC User Manual

3.4 Serial Ports

CPU Module Datasheet: CPUE05
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. Port 1 can also be configured for
Local Station Manager operation to provide access to diagnostic information about the
Ethernet interface. 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.
Port 1 can be configured for either CPU serial communications (SNP,
RTU, Serial I/O), or local Station Manager use. If Port 1 has been
configured for CPU use, it can be forced to local Station Manager
operation using the Restart pushbutton. Once forced, Port 1 remains
available for station manager use until the PLC is power cycled, or the
Restart pushbutton is pressed. If Port 1 is configured as a local Station
Manager, it cannot be used for CPU serial communications or for
firmware upgrades using Winloader. The Restart pushbutton will NOT
toggle it to the CPU serial protocols.
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). Port 2 can be used for program, configuration, and
table updates with the EZ Program Store module.
The following table compares the functions of Port 1 and Port 2.
CPU Protocols (SNP slave,
RTU master/slave, Serial I/O)
Local Station Manager
Firmware Upgrade
Smart module firmware
upgrade
EZ Program Store device
Port 1
Defaults to SNP slave
Yes (see above)
PLC in Stop/No I/O
mode, Port 1 not disabled
or in Local Station
Manager mode.
PLC in Stop/No I/O
mode, Port 1 configured
for CPU protocol
No
GFK-1503E User Manual 43
Port 2
Defaults to SNP slave
No
No
PLC must be in Stop/No
IO mode.
Read, Write, Verify, and
Update. PLC must be in
Stop/No IO mode.