Rainbow-electronics ATmega163L Manuel d'utilisateur télécharger pdf (Page 85)

ATmega163(L)

Figure 55. Formats and States in the Slave Transmitter Mode

Assembly Code Example - Slave Transmitter Mode

; Part specific include file and TWI include file must be included.

; <Initialize registers, including TWAR, TWBR and TWCR>

ldi r16, (1<<TWINT) | (1<<TWEA) | (1<<TWEN)

out TWCR, r16 ; Enable TWI in Slave Transmitter Mode

; <Receive START condition and SLA+R>

wait14: in r16,TWCR ; Wait for TWINT flag set. This indicates that

sbrs r16, TWINT ; SLA+R has been received, and ACK/NACK has

rjmp wait14 ; been returned

in r16, TWSR ; Check value of TWI Status Register. If status

cpi r16, ST_SLA_ACK ; different from ST_SLA_ACK, go to ERROR

brne ERROR

ldi r16, 0x33 ; Load data (here, data = 0x33) into TWDR register

out TWDR, r16

ldi r16, (1<<TWINT) | (1<<TWEA) | (1<<TWEN)

out TWCR, r16 ; Clear TWINT bit in TWCR to start transmission of data.

; Setting TWEA indicates that ACK

; should be received when transfer finished

; <Send more data bytes if needed>

wait15: in r16,TWCR ; Wait for TWINT flag set. This indicates that

sbrs r16, TWINT ; data has been transmitted, and ACK/NACK has

rjmp wait15 ; been received

S SL A R A DATA A

$A8 $B8

$B0

Reception of the own

slave address and one or

more data bytes

Last data byte transmitted.

Switched to not addressed

slave (TWEA = '0')

Arbitration lost as master

and addressed as slave

From master to slave

From slave to master

Any number of data bytes

and their associated acknowledge bits

This number (contained in TWSR) corresponds

to a defined state of the 2-Wire Serial Bus

P or SDATA

$C0

DATA A

$C8

P or SAll 1's

1 2 ... 80 81 82 83 84 85 86 87 88 89 90 ... 155 156

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Rainbow-electronics ATmega163L Manuel d'utilisateur Page 85

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