Rainbow-electronics ATmega163L Instrukcja Użytkownika Pobierz pdf (Strona 86)

ATmega163(L)

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

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

brne ERROR

ldi r16, 0x44 ; Load data (here, data = 0x44) 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

wait16: in r16,TWCR ; Wait for TWINT flag set. This indicates that

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

rjmp wait16 ; been received

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

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

brne ERROR

ldi r16, 0x55 ; Load data (here, data = 0x55) into TWDR register

out TWDR, r16

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

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

; Not setting TWEA indicates that

; NACK should be received after data byte (Master

; signalling end of transmission)

wait17: in r16,TWCR ; Wait for TWINT flag set. This indicates that

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

rjmp wait17 ; been received

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

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

brne ERROR

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

out TWCR, r16 ; Continue address reckognition in Slave Transmitter mode

Table 36. Status Codes for Miscellaneous States

Status code

(TWSR)

Status of the 2-wire Serial Bus

and 2-wire Serial Interface

hardware

Application software response

Next action taken by 2-wire Serial Interface hardware

To/from TWDR

To TWCR

STA STO TWINT TWEA

$F8 No relevant state information

available; TWINT = ‘0’

No TWDR action No TWCR action Wait or proceed current transfer

$00 Bus error due to an illegal

START or STOP condition

No TWDR action 0 1 1 X Only the internal hardware is affected, no STOP condi-

tion is sent on the bus. In all cases, the bus is released

and TWSTO is cleared.

1 2 ... 81 82 83 84 85 86 87 88 89 90 91 ... 155 156

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