80C186EB/80C188EB Microprocessor User's Manual - CEUNES

SERIAL COMMUNICATIONS UNIT10.5 SERIAL PORT EXAMPLESThis section contains examples that show ways to use the serial port.NOTEThe examples assume that the Peripheral Control Block is located in I/O space.10.5.1 Asynchronous Mode ExampleExample 10-1 contains sample code to initialize Serial Port 0 for 9600-baud operation in asynchronousMode 4.$mod186namescu_async_example;;This file contains an example of initialization code for the 80C186EB;Serial Communications Unit. The example has three procedures:;ASYNC_CHANNEL_SETUP sets up channel 0 as 9600 baud, full duplex,; 7 data bits+parity, with CTS# control.;ASYNC_REC_INT_PROC is an interrupt handler for a reception. The procedure; is nearly empty, since the code to perform error checking; and receive buffer handling is application dependent.;ASYNC_XMIT_INT_PROC is an interrupt handler for a transmission. This; procedure, too, is nearly devoid of code. A typical; application would test the TXE bit, then copy data from; the transmit buffer in memory to the S0TBUF register.;We assume serial port registers have been correctly defined and the PCB; is located in I/O space.B0CMP equ 0xxxx ;channel 0 baud rate compareS0CON equ 0xxxx ;channel 0 controlS0STS equ 0xxxx ;channel 0 statusS0RBUF equ 0xxxx ;channel 0 receive bufferS0TBUF equ 0xxxx ;channel 0 transmit bufferRI_TYPE equ xx ;receive is interrupt type 20TI_TYPE equ 21 ;transmit is interrupt type 21EOI equ 0ff02h ;end-of-interrupt registerSCUCON equ 0ff14h ;SCU interrupt control registercode_segassumesegment publiccs:code_segASYNC_CHANNEL_SETUP proc near;First, set up the interrupt handler vectorsxor ax,axmov ds,ax ;need DS to point to interrupt vector;table at 0hmov bx,RI_TYPE*4mov ax,offset ASYNC_REC_INT_PROCmov [bx],axmov ax, seg ASYNC_REC_INT_PROCmov [bx+2],axExample 10-1. Asynchronous Mode 4 Example10-23