DAC8562
DAC8562 – M68HC11 Interface Program Source Code
*
DAC8562–M68HC11 Interface Program Source Code (Continued)
* Update DAC output with contents of input registers
* DAC8562 to M68HC11 Interface Assembly Program
*
* Adolfo A. Garcia
* September 14, 1992
*
DUMP
*
BCLR PORTC,Y $02
BSET PORTC,Y $02
Assert CE/
Latch DAC register
* M68HC11 Register definitions
*
PULA
PULY
PULX
RTS
When done, restore registers X, Y & A
** Return to Main Program **
PORTB
PORTC
*
EQU
EQU
$1004
$1003
Port C control register
“0,0,0,0;0,CLR/,CE/,MSB-LSB/”
Port C data direction
DDRC
*
EQU
$1007
* RAM variables:
MSBS are encoded from 0 (Hex) to F (Hex)
LSBS are encoded from 00 (Hex) to F (Hex)
DAC requires two 8-bit loads
*
*
*
MSBS
LSBS
EQU
EQU
$00
$01
Hi-byte: “0,0,0,0;MSB,DB10,DB9,DB8”
Lo-byte: “DB7,DB6,DB5,DB4;DB3,DB2,
DB1,DB0”
*
* Main Program
*
ORG
LDS
$C000
#$CFFF
Start of user’s RAM in EVB
Top of C page RAM
INIT
*
* Initialize Port C Outputs
*
LDAA #$07
STAA DDRC
0,0,0,0;0,1,1,1
CLR/,CE/, and MSB-LSB/ are now enabled
as outputs
LDAA #$06
0,0.0,0;0,1,1,0
*
CLR/-Hi, CE/-Hi, MSB-LSB/-Lo
Initialize Port C Outputs
STAA PORTC
*
* Call update subroutine
*
BSR
JMP
UPDATE
$E000
Xfer 2 8-bit words to DAC8562
Restart BUFFALO
*
* Subroutine UPDATE
*
UPDATE PSHX
Save registers X, Y, and A
PSHY
PSHA
*
* Enter contents of the Hi-byte input register
*
LDAA #$0A
STAA MSBS
0,0,0,0;1,0,1,0
MSBS are set to 0A (Hex)
*
* Enter Contents of’ Lo-byte input register
*
LDAA #$AA
STAA LSBS
1,0,1,0;1,0,1,0
LSBS are set to AA (Hex)
*
LDX
LDY
#MSBS
#$1000
Stack pointer at 1st byte to send via Port B
Stack pointer at on-chip registers
*
* Clear DAC output to zero
*
BCLR PORTC,Y $04
BSET PORTC,Y $04
Assert CLR/
De-assert CLR/
*
* Loading input buffer latches
*
BSET PORTC,Y $01
LDAA 0,X
STAA PORTB
INX
Set hi-byte register load
TFRLP
Get a byte to transfer via Port B
Write data to input register
Increment counter to next byte for transfer
Are we done yet ?
If yes, update DAC output
Latch hi-byte register and set lo-byte register
load
CPX
BEQ
#LSBS+1
DUMP
BCLR PORTC,Y $01
BRA TFRLP
*
REV. A
–15–
ADI [ ADI ]
