\prog;Xi2cT0.asm|Simple write test
;JDN 280301 
.Proc	16F84
RB0	= 5	; bit on Status register that control Bank1
.Macro	Bank0to1
	Set	Status:#RB0
.Endmacro
.Macro	Bank1to0
	Clr	Status:#RB0
.Endmacro

\b;PortA
bSCK	= 0	; I2C bits
bSDA	= 1
DirA	= 2'00011	; Bits 0 and 1 as inputs
PortI2C	= 5
TrisI2C	= Porti2c

SlaveAddress = 16'70	; 8574 I/O expander

.Ins	Xi2cM.asi	; Inserts I2C macros

\b;PortB
bLed	= 0	; Led bright if output=0
DirB	=2'00000000	; Bit 0 as output
.Macro	LedOn
	Clr	PortB:#bLed
.Endmacro
.Macro	LedOff
	Set	PortB:#bLed
.Endmacro

\b;Variables
.Loc	16'0C	; begin of variables
ADi2c:	.Blk.16	1
CBit:	.Blk.16	1

\b;Programme
.Loc	0	; program start
Deb:	Move	#DirA,W
	Move	W,TrisA
	Move	#DirB,W
	Move	W,TrisB
	Clr	PortI2C	; important for SCK SDA

Loop:	Move	#SlaveAddress,W
	Move	W,ADi2c
	Call	WriteI2C
	Skip,CS
	LedOn		; Ack
	Skip,CC
	LedOff		; NAck
	Call	Wait	; space on the scope
			; to ease synchronization
	Jump	Loop

\rout;WrI2C|Send address or data
; Duration about 100 \mu;s
\in;ADi2c   byte to be transmitted
\out;Carry = 0 si ack 
\mod:ADi2c
WriteI2C:
	Start
	Move	#8,W
	Move	W,CBit
 L$:	RLC	ADi2c
	Skip,CC
	SetSDA
	Skip,CS
	ClrSDA
	FullSCk
	DecSkip,EQ  CBit
	Jump	L$
	SetSDA	; On attend un Ack
	ClrC
	Bank1to0	; Acknowledge
	TestSkip,BC PortI2C:#bSDA	; CK doit être à 0
	SetC
	Bank0to1
	FullSCK
	Nop3
	ClrSDA
	Stop
	Ret

\rout:Wait|1ms wait
Wait:	Clr	W
 W$:	Add	#-1,W	; 4 us loop
	Skip,EQ  	; repeated 256 times
	Jump	W$
	Ret
.End