Contec SPI-8450-LLVA User Manual

CHAPTER 3 – Jumper setting

SPI-8450-LLVA

3.2

RS-232C/422/485 Selector: JRS1 & JRS2

RS-232C

JRS2 JRS1

10 8 6 4 2 2 4 6 8 10 12 14 16 18 20 22 24

9 7 5 3 1 1 3 5 7 9 11 13 15 17 19 21 23

RS-422

JRS2 JRS1

10 8 6 4 2 2 4 6 8 10 12 14 16 18 20 22 24

9 7 5 3 1 1 3 5 7 9 11 13 15 17 19 21 23

RS-485

JRS2 JRS1

10 8 6 4 2 2 4 6 8 10 12 14 16 18 20 22 24

9 7 5 3 1 1 3 5 7 9 11 13 15 17 19 21 23

1. For RS-485, TX+(pin 2) and RX+ (pin 3) must jumper together

inside the D type connector.

2. TX- (pin 1) and RX- (pin 4) is the same.

Transmit date control in half-duplex mode

In half-duplex mode, the transmission buffer must be controlled to prevent transmit data

from causing a collision. The SPI-8450-LLVA uses the RTS signal and bit 1 in the modem
control register to control transmit data.

Modem control register

(Setting I/O address +4H) bit 1: 0 … RTS High (Disables transmission)

1 … RTS low (Enables transmission)