Typewriter User Manual

7- 48 MC68340 USER’S MANUAL MOTOROLA
* Serial register offsets from serial base address
MR1A EQU $10 Mode register 1 A
MR2A EQU $20 Mode register 2 A
SRA EQU $11 Status register A
CSRA EQU $11 Clock select reg A
CRA EQU $12 Command reg A
ACR EQU $14 Auxiliary control reg
OPCR EQU $1D Output port control reg
OP_BS EQU $1E Output port bit set (write 1 to set)
OP_BR EQU $1F Output port bit reset (write 1 to clear)
***************************************************************************
***************************************************************************
* Initialize Serial channel A
***************************************************************************
LEA MODBASE+SERIAL,A0 Pointer to serial channel A
* Module configuration register:
* Enable serial module for normal operation, ignore FREEZE, select the
* crystal clock. Supervisor/user serial registers unrestricted.
* Interrupt arbitration at priority $02.
MOVE.B #$00,MCRH(A0)
MOVE.B #$02,MCRL(A0)
* WAIT FOR TRANSMITTER EMPTY (OR TIMEOUT)
MOVE.W #$2000,D0 init loop counter
XBMTWAIT EQU *
BTST #3,SRA(A0) TX empty in status reg?
NOP
DBNE D0,XBMTWAIT loop until set or timeout
* NEGATE
RTSA SIGNAL OUTPUT
MOVE.B #0,OPCR(A0) make OP0-7 general purpose
MOVE.B #$01,OP_BR(A0) clear
RTSA/OP0 output
* RESET RECEIVER/TRANSMITTER
MOVE.B #$20,CRA(A0) Issue reset receiver command
MOVE.B #$30,CRA(A0) Issue reset transmitter command
* SET BAUD RATE SET 2
MOVE.B #$80,ACR(A0)
* MODE REGISTER 1
MOVE.B #$93,MR1A(A0) 8 bits, no parity, auto RTS control
Frees
cale Semiconductor,
I
Freescale Semiconductor, Inc.
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