Contec bx200 SERIES, User Manual

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4. Each Component Function
BX-2x0-DCxxxx, BX-2x0D-DCxxxx User’s manual
37
Controlling RS-485 communication
I/O ports use address 2a0/2a4h.
This section gives examples of flowcharts and programming related to switching enable signals for
transmission/reception.
Terminating resistor on/off settings are performed from the BIOS setup screen. Refer to Chapter 5, "BIOS
Setup", and adjust settings as necessary.
(1) Example flowchart
Open
: Outputs command 87h to port 2a0h two times.
Output
: Outputs command 93h to port 2a0h and then outputs settings data to port 2a0h.
Close
: Outputs command aah to port 2a0h.
(2) Example programming
The following example is written in Intel 8086 assembly language.
The utility in IPC-SLIB-01 allows you to use this language in Windows.
(For the latest version of IPC-SLIB-01, visit the CONTEC website.)
;-------------------------------------------
;Open
;-------------------------------------------
CHK_OPEN1:
MOV
DX,2A4H
IN AL,DX
TEST AL,2 ;Check status of output
JNZ CHK_OPEN1
MOV DX,2A0H
MOV AL,87H ;Open Command
OUT DX,AL
CHK_OPEN2:
MOV
DX,2A4H
IN AL,DX
TEST AL,2 ;Check status of output
JNZ CHK_OPEN2
MOV DX,2A0H
MOV AL,87H ;Open Command
OUT DX,AL
CHK_OPEN3: ;Check status of input
MOV DX,2A4H
IN AL,DX
TEST AL,1
JZ CHK_OPEN3
MOV DX,2A0H
IN AL,DX ;Open success if AL = AAH
;-------------------------------------------
;Set TX/RX