Chapter 6. Serial I/O, SNP & RTU Protocols
GFK-2222AD
April 2018
217
6.2.10
Write Port Control Function (4304)
This function controls output signals on the specified port:
Example Command Block for the Write Port Control Function
VALUE
(decimal)
VALUE
(hexadecimal)
MEANING
Address
0002
0002
Data block length
A1
0000
0000
NOWAIT mode
A2
0008
0008
Status word memory type (%R)
A3
0000
0000
Status word address minus 1 (%R0001)
A4
0000
0000
Not used
A5
0000
0000
Not used
A6
4304
10D0
Write port control command
A7
xxxx
xxxx
Port control word
Port Control Word
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RTS DTR --
--
--
--
--
--
--
--
--
--
--
--
--
--
Port Control Word Meanings:
15
RTS
Commanded state of Request to Send signal
1 = Activates RTS
0 = Deactivates RTS
14
DTR
Commanded state of Data Terminal Ready signal
1 = Activates DTR
0 = Deactivates DTR
13-0
n/a
Unused (should be zero)
Operating Notes
For reference, see the tables under
Support for the DTR output signal is provided for COM1 only, on all RX7i and RX3i models (except CPE302,
CPE305, CPE330 and CPE400), in Rel 7.16 and later releases.
For CPU COM2 (RS-485), the RTS signal is also controlled by the transmit driver. Therefore, control of RTS
is dependent on the current state of the transmit driver. If the transmit driver is not enabled, asserting
RTS with the Write Port Control COMMREQ will not cause RTS to be asserted on the serial line. The state
of the transmit driver is controlled by the protocol and is dependent on the current Duplex Mode of the
port. For 2-wire and 4-wire Duplex Mode, the transmit driver is only enabled during transmitting.
Therefore, RTS on the serial line will only be seen active on COM2 (configured for 2-wire or 4-wire Duplex
Mode) when data is being transmitted. For point-to-point Duplex Mode, the transmit driver is always
enabled. Therefore, in point-to-point Duplex Mode, RTS on the serial line will always reflect what is
chosen with the Write Port Control COMMREQ.
