Rainbow-electronics ATmega128L Manual de usuario descargar pdf (Pagina 203)

203

ATmega128(L)

2467B–09/01

Note: For I/O registers located in extended I/O map, “IN”, “OUT”, “SBIS”, “SBIC”, “CBI”, and “SBI” instructions must be replaced with

instructions that allow access to extended I/O. Typically “LDS” and “STS” combined with “SBRS”, “SBRC”, “SBR”, and “CBR”.

Assembly Code Example C Example Comments

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

(1<<TWEN)

out TWCR, r16

TWCR = (1<<TWINT)|(1<<TWSTA)|

(1<<TWEN) Send START condition

wait1:

in r16,TWCR

sbrs r16,TWINT

rjmp wait1

while (!(TWCR & (1<<TWINT)))

;

Wait for TWINT flag set. This indicates that

the START condition has been transmitted

in r16,TWSR

andi r16, 0xF8

cpi r16, START

brne ERROR

if ((TWSR & 0xF8) != START)

ERROR();

Check value of TWI Status Register. Mask

prescaler bits. If status different from START

go to ERROR

ldi r16, SLA_W

out TWDR, r16

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

out TWCR, r16

TWDR = SLA_W;

TWCR = (1<<TWINT) | (1<<TWEN);

Load SLA_W into TWDR register. Clear

TWINT bit in TWCR to start transmission of

address

wait2:

in r16,TWCR

sbrs r16,TWINT

rjmp wait2

while (!(TWCR & (1<<TWINT)))

;

Wait for TWINT flag set. This indicates that

the SLA+W has been transmitted, and

ACK/NACK has been received.

in r16,TWSR

andi r16, 0xF8

cpi r16, MT_SLA_ACK

brne ERROR

if ((TWSR & 0xF8) != MT_SLA_ACK)

ERROR();

Check value of TWI Status Register. Mask

prescaler bits. If status different from

MT_SLA_ACK go to ERROR

ldi r16, DATA

out TWDR, r16

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

out TWCR, r16

TWDR = DATA;

TWCR = (1<<TWINT) | (1<<TWEN);

Load DATA into TWDR register. Clear TWINT

bit in TWCR to start transmission of address

wait3:

in r16,TWCR

sbrs r16,TWINT

rjmp wait3

while (!(TWCR & (1<<TWINT)))

;

Wait for TWINT flag set. This indicates that

the DATA has been transmitted, and

ACK/NACK has been received.

in r16,TWSR

andi r16, 0xF8

cpi r16, MT_DATA_ACK

brne ERROR

if ((TWSR & 0xF8) != MT_DATA_ACK)

ERROR();

Check value of TWI Status Register. Mask

prescaler bits. If status different from

MT_DATA_ACK go to ERROR

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

(1<<TWSTO)

out TWCR, r16

TWCR = (1<<TWINT)|(1<<TWEN)|

(1<<TWSTO); Transmit STOP condition

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