AT90CAN128-16AE ATMEL Corporation, AT90CAN128-16AE Datasheet - Page 213

• Manufacturer Part Number: AT90CAN128-16AE
• Description: 8-bit Avr Microcontroller With 128K Bytes of Isp Flash And CAN Controller.flash (Kbytes) 128 Vcc (V) 2.7-5.5 EEPROM (Kbytes) 4 SRAM (bytes) 4K CAN (mess. Obj.) 15
• Manufacturer: ATMEL Corporation

4250C–CAN–03/04
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Assembly Code Example
ldi
sts
wait1:
lds
sbrs r16,TWINT
rjmp wait1
lds
andi r16, 0xF8
cpi
brne ERROR
ldi
sts
ldi
sts
wait2:
lds
sbrs r16,TWINT
rjmp wait2
lds
andi r16, 0xF8
cpi
brne ERROR
ldi
sts
ldi
sts
wait3:
lds
sbrs r16,TWINT
rjmp wait3
lds
andi r16, 0xF8
cpi
brne ERROR
ldi
sts
r16, (1<<TWINT)|(1<<TWSTA)|
(1<<TWEN)
TWCR, r16
r16,TWCR
r16,TWSR
r16, START
r16, SLA_W
TWDR, r16
r16, (1<<TWINT) | (1<<TWEN)
TWCR, r16
r16,TWCR
r16,TWSR
r16, MT_SLA_ACK
r16, DATA
TWDR, r16
r16, (1<<TWINT) | (1<<TWEN)
TWCR, r16
r16,TWCR
r16,TWSR
r16, MT_DATA_ACK
r16, (1<<TWINT)|(1<<TWEN)|
(1<<TWSTO)
TWCR, r16
In the following an assembly and C implementation of the example is given. Note that
the code below assumes that several definitions have been made for example by using
include-files.
set. Writing a one to TWINT clears the flag. The TWI will then commence executing
whatever operation was specified by the TWCR setting.
C Example
TWCR = (1<<TWINT)|(1<<TWSTA)|
while (!(TWCR & (1<<TWINT)))
if ((TWSR & 0xF8) != START)
TWDR = SLA_W;
TWCR = (1<<TWINT) | (1<<TWEN);
while (!(TWCR & (1<<TWINT)))
if ((TWSR & 0xF8) != MT_SLA_ACK)
TWDR = DATA;
TWCR = (1<<TWINT) | (1<<TWEN);
while (!(TWCR & (1<<TWINT)))
if ((TWSR & 0xF8) != MT_DATA_ACK)
TWCR = (1<<TWINT)|(1<<TWEN)|
(1<<TWEN)
(1<<TWSTO);
;
ERROR();
;
ERROR();
;
ERROR();
Comments
Send START condition
Wait for TWINT flag set. This indicates that
the START condition has been transmitted
Check value of TWI Status Register. Mask
prescaler bits. If status different from START
go to ERROR
Load SLA_W into TWDR Register. Clear
TWINT bit in TWCR to start transmission of
address
Wait for TWINT flag set. This indicates that
the SLA+W has been transmitted, and
ACK/NACK has been received.
Check value of TWI Status Register. Mask
prescaler bits. If status different from
MT_SLA_ACK go to ERROR
Load DATA into TWDR Register. Clear TWINT
bit in TWCR to start transmission of data
Wait for TWINT flag set. This indicates that
the DATA has been transmitted, and
ACK/NACK has been received.
Check value of TWI Status Register. Mask
prescaler bits. If status different from
MT_DATA_ACK go to ERROR
Transmit STOP condition
AT90CAN128
213