Cirrus Logic AN131 - Manual (Page 6)

AN131
6 AN131REV2
6. APPENDIX: 68HC05 MICROCODE TO INTERFACE TO THE CS5521/22/23/24/28
;*****************************************************************************
;* File:
55226805.ASM
;* Date: September 23, 1998
;* Revision:0
;* Processor:68HC05
;*
;* Program entry point at routine ’main’. Entry point address is $100
;*
;* This program is an example on how to interface a 68HC05 Microcontroller
;* to a CS5521/22/23/24/28 ADC. The program interfaces via the SPI port (Port D)
;* on the microcontroller, which controls the serial communications,
;* calibration, and conversion cycles.
;*****************************************************************************
;*** Memory Map Equates ***
PORTA EQU $00 ;General Purpose I/O Port
DDRA EQU $04 ;Data Direction Control for Port A
PORTD EQU $03 ;Port D Direct Pin Access (Input)
SPCR EQU $0A ;Serial Peripheral Control Register
SPSR EQU $0B ;Serial Peripheral Status Register
SPDR EQU $0C ;Serial Peripheral Data I/O Register
SPIF EQU 7 ;Serial Peripheral Data Transfer Flag
;*** RAM Values ***
ORG $50
HIGHBYTE RMB 1 ;Upper 8 bits of Conversion Register
MIDBYTE RMB 1 ;Middle 8 bits of Conversion Register
LOWBYTE RMB 1 ;Lower 8 bits of Conversion Register
COMMAND RMB 1 ;Command Byte storage location
;*****************************************************************************
;* Program Code
;*****************************************************************************
ORG $100
;*****************************************************************************
;* Routine - main
;* Input
- none
;* Output - none
;* This is the entry point and the main loop of the program.
;*****************************************************************************