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AN 114

Application Note

www.xicor.com

REV 1.1 11/12/02

clr

SCL

;Complete clock pulse

ret

;-----------------------------------------------------------------------------

;

; NAME: stop_cond (Stop condition)

; FUNCTION: Issues an I2C bus stop condition

; INPUTS: NONE

; OUTPUTS: NONE

; CALLS: NONE

; AFFECTED: SDA, SCL

;

;-----------------------------------------------------------------------------

stop_cond:

clr

SDA

; Pull SDA LOW and hold

setb

SCL

; Pull SCL HIGH and hold

nop

nop

nop

nop

setb

SDA

; Pull SDA HIGH (SCL=HIGH)

ret

;-----------------------------------------------------------------------------

;

; NAME: ack_send (Send Acknowledge)

; FUNCTION: Sends an acknowledge bit to complete SDA line data reads

; INPUTS: NONE

; OUTPUTS: NONE

; CALLS: send_bit

; AFFECTED: A

;

;-----------------------------------------------------------------------------

ack_send:

clr

a

; A <- LOW (Sending a 0)

call

SEND_BIT

; Send the bit!

ret

;-----------------------------------------------------------------------------

;

; NAME: polling (Acknowledge polling for XFR_WCR, WRITE_DR, GXFR_WCR)

; FUNCTION: Sends dummy commands to X9408 during an internal write cycle

;

so that the end of the cycle is marked by an acknowledge

; INPUTS: ADDR_BYTE

; OUTPUTS: NONE

; CALLS: start_cond, send_byte

; AFFECTED: C

;

;-----------------------------------------------------------------------------

polling:

call

START_COND

; Re-establish I2C protocol

mov

a,ADDR_BYTE

; Attempt to send a dummy command

again:

call

SEND_BYTE

jc

POLLING

; If C=1, then there was no ACK

ret