;-----------------------------------------------------------------------------
; Copyright (C) 2001 CYGNAL INTEGRATED PRODUCTS, INC.
; All rights reserved.
;
; FILE NAME : SPI_MODE0.ASM
; DATE : 14 DEC 01
; TARGET MCU : C8051F30x
; DESCRIPTION : This is a function which implements a master SPI port on
; the C8051F30x series of devices. The function can
; be called from a C program with the following function
; prototype:
;
; extern char SPI_Transfer (char);
;
; NOTES : Timing is as follows (Mode 0 SPI):
; Parameter SYSCLKs
; MOSI valid to SCK rising 2
; SCK rising to MISO Latch 2
; SCK falling to MOSI valid 5
; SCK high time 5
; SCK low time 7
;
;-----------------------------------------------------------------------------
NAME SPI_MODE0
?PR?_SPI_Transfer?SPI_MODE0 SEGMENT CODE
PUBLIC _SPI_Transfer
$include (c8051f300.inc) ; Include regsiter definition file.
$include (SPI_defs.h) ; Include sbit definitions for SPI
RSEG ?PR?_SPI_Transfer?SPI_MODE0
_SPI_Transfer:
USING 0
MOV A, R7 ; Store passed variable in A
MOV R7, #08H ; Load R7 to count bits
RLC A ; Rotate MSB into Carry Bit
SPI_Loop: MOV MOSI, C ; Move bit out to MOSI
SETB SCK ; Clock High
MOV C, MISO ; Move MISO into Carry Bit
RLC A ; Rotate Carry Bit into A
CLR SCK ; Clock Low
DJNZ R7, SPI_Loop ; Loop for another bit until finished
MOV R7, A ; Store return value in R7
?C0001:
RET ; Return from routine
END ; END OF FILE