30
The NPC-486E supports two RS-485 channels: an input and an output. These channels
correspond to the Transmit and Receive Data of the COM2 serial port. The on-board
connector, J8, for COM2 is a 14-pin, dual-in-line, male header. The RS-485 transmit and
receive channel pin-out for J8 is:
Pin #
Signal
Pin #
Signal
1
NC
2
NC
3
NC
4
NC
5
NC
6
NC
7
NC
8
NC
9
GND
10
NC
11
RS485 TXD +
12
RS485 TXD -
13
RS485 RXD +
14
RS485 RXD -
The selection of RS-485 versus RS-232 drive types is controlled by bit 4 in the NPC-486E
Custom I/O Register 0. A “1” on this bit disables RS-485 and selects RS-232; a “0” on
this bit selects RS-485.
7
6
5
4
3
2
1
0
C u s t o m R e g ister #0
B it
H a lf D u p l e x T r a n s m i t C o n t r o l
0 : RS -2 3 2 (default)
1 : RS -4 8 5
In a half duplex system the transmit and receive functions share pins 13 and 14 of J8. Bit
4 of Custom I/O register 0 is used to control the transmit enable in half duplex systems.
Transmitter
Differential
Data
Out
Custom Register 0
Bit 5
T+
T-
R-
R+
Data
In
J8 Pin 13
J8 Pin 14
8.3.1 RS-485 Multi-drop
