;
;	Starting with ATMEL 89C51ED2 and SPI
;
;
;
;
;
;

$NOMOD
$TITLE(BYTE SPI_TEST)
$DEBUG
$OBJECT
$NOPAGING

;Variable declarations

$include(C:\asm51\89C51ED2.inc)

SS	EQU	P1.1
rec_data DATA 08H
trans_completed bit 00h



org 0000H
ljmp MAIN

org 4Bh
ljmp SPI_INT

org 100h
MAIN:
	orl spcon, #10h ;SPI Master
	setb SS
	orl spcon, #82h ;Speed xtal/128
	anl spcon, #0F7h ;cpol = 1
	orl spcon, #04h  ;cpha = 1
	orl spcon, #20h  ;SS disabled
	orl ien1, #04h   ;SPI Interrupt enabled
	orl spcon, #40h  ;run SPI
	clr trans_completed
	setb ea
	
	

;///////////////////////////////////////////////////////////////
;
;  Set up MAX6957 registers
;
 
	
	clr SS
	
	mov SPDAT,#04h		; config register
   	jnb trans_completed,$	; /* wait end of transmission */
   	clr trans_completed	; /* clear software transfer flag */
	
   	mov SPDAT,#01h		; disable shutdown, global current control, trans det disabled
   	jnb trans_completed,$	; /* wait end of transmission */
   	clr trans_completed	; /* clear software transfer flag */
   	
   	setb SS			; read 2 bytes into SPI slave
	nop	
	nop
	nop			; min CS pulse is 19 ns so at 12 MHz one nop should do it
	clr SS
	
	mov SPDAT,#0Dh		; ports 20, 21, 22, 23 config register
   	jnb trans_completed,$	; /* wait end of transmission */
   	clr trans_completed	; /* clear software transfer flag */
	
   	mov SPDAT,#9Ch		; set port 22 to output
   	jnb trans_completed,$	; /* wait end of transmission */
   	clr trans_completed	; /* clear software transfer flag */
   	
   	   	
   	setb SS			; read 2 bytes into SPI slave
	nop		
	nop
	nop			; min CS pulse is 19 ns so at 12 MHz one nop should do it
	clr SS
   	
;/////////////////////////////////////////////////////////////
;
;  Set port 22 on
;   	
   	
   	mov SPDAT,#36h		; port 22
   	jnb trans_completed,$	; /* wait end of transmission */
   	clr trans_completed	; /* clear software transfer flag */
	
   	mov SPDAT,#01h		; on
   	jnb trans_completed,$	; /* wait end of transmission */
   	clr trans_completed	; /* clear software transfer flag */

   	setb SS	
	clr p2.0		; Debugging

	jmp $ 		; sit and stay
	
SPI_INT:			;  /* interrupt address is 0x004B */
	
	mov R7,SPSTA
	mov ACC,R7
	jnb ACC.7,BREAK1 		;case 0x80: data transfer complete
	mov rec_data,SPDAT 	;  /* read receive data */
    setb trans_completed 	;  /* set software flag */
BREAK1:

	jnb ACC.4,BREAK2 		;case 0x10: Mode fault
		;  /* put here for mode fault tasking */	
BREAK2:
	
	jnb ACC.6,BREAK3 		;case 0x40: Write Collision
		;  /* put here for overrun tasking */	
BREAK3:

RETI

	
END