Motorola Espresso Maker MC68340 Benutzerhandbuch

7- 48

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

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Freescale Semiconductor, Inc.

For More Information On This Product,

   Go to: www.freescale.com

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