AD8801 datasheet(13/16 Pages) AD

13 / 16 page

AD8801/AD8803

REV. A

–13–

* AD8801/AD8803 to M68HC11 Interface Assembly Program

* M68HC11 Register definitions

PORTC

EQU

$1003

Port C control register

“0,0,0,0;0,0,RS/, SHDN/”

DDRC

EQU

$1007

Port C data direction

PORTD

EQU

$1008

Port D data register

“0,0,/CS,CLK;SDI,0,0,0”

DDRD

EQU

$1009

Port D data direction

SPCR

EQU

$1028

SPI control register

“SPIE,SPE,DWOM,MSTR;CPOL,CPHA,SPR1,SPR0”

SPSR

EQU

$1029

SPI status register

“SPIF,WCOL,0,MODF;0,0,0,0”

SPDR

EQU

$102A

SPI data register; Read-Buffer; Write-Shifter

* SDI RAM variables:

SDI1 is encoded from 0 (Hex) to 7 (Hex)

SDI2 is encoded from 00 (Hex) to FF (Hex)

AD8801/3 requires two 8-bit loads; upper 5 bits

of SDI1 are ignored. AD8801/3 address bits in last

three LSBs of SDI1.

SDI1

EQU

$00

SDI packed byte 1 “0,0,0,0;0,A2,A1,A0”

SDI2

EQU

$01

SDI packed byte 2 “DB7,DB6,DB5,DB4;DB3,DB2,DB1,DB0”

* Main Program

ORG

$C000

Start of user’s RAM in EVB

INIT

LDS

#$CFFF

Top of C page RAM

* Initialize Port C Outputs

LDAA

#$03

0,0,0,0;0,0,1,1

/RS-Hi, /SHDN-Hi

STAA

PORTC

Initialize Port C Outputs

LDAA

#$03

0,0,0,0;0,0,1,1

STAA

DDRC

/RS and /SHDN are now enabled as outputs

* Initialize Port D Outputs

LDAA

#$20

0,0,1,0;0,0,0,0

/CS-Hi,/CLK-Lo,SDI-Lo

STAA

PORTD

Initialize Port D Outputs

LDAA

#$38

0,0,1,1;1,0,0,0

STAA

DDRD

/CS,CLK, and SDI are now enabled as outputs

* Initialize SPI Interface

LDAA

#$53

STAA

SPCR

SPI is Master,CPHA=0,CPOL=0,Clk rate=E/32

* Call update subroutine

BSR

UPDATE

Xfer 2 8-bit words to AD8402

JMP

$E000

Restart BUFFALO

* Subroutine UPDATE

UPDATE

PSHX

Save registers X, Y, and A

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