ata5773 ATMEL Corporation, ata5773 Datasheet - Page 172

• Manufacturer Part Number: ata5773
• Description: Microcontroller With Uhf Ask/fsk Transmitter
• Manufacturer: ATMEL Corporation

14.3.3
120
ATtiny24/44/84
SPI Slave Operation Example
The code is size optimized using only eight instructions (plus return). The code example
assumes that the DO and USCK pins have been enabled as outputs in DDRA. The value stored
in register r16 prior to the function is called is transferred to the slave device, and when the
transfer is completed the data received from the slave is stored back into the register r16.
The second and third instructions clear the USI Counter Overflow Flag and the USI counter
value. The fourth and fifth instructions set three-wire mode, positive edge clock, count at USITC
strobe, and toggle USCK. The loop is repeated 16 times.
The following code demonstrates how to use the USI as an SPI master with maximum speed
(f
The following code demonstrates how to use the USI module as a SPI Slave:
SCK
SPITransfer_Fast:
ret
init:
= f
CK
sbrs
rjmp
in
ret
out
ldi
ldi
out
out
out
out
out
out
out
out
out
out
out
out
out
out
out
out
in
ldi
out
/2):
r16, USIOIF
SPITransfer_loop
r16,USIDR
USIDR,r16
r16,(1<<USIWM0)|(0<<USICS0)|(1<<USITC)
r17,(1<<USIWM0)|(0<<USICS0)|(1<<USITC)|(1<<USICLK)
USICR,r16 ; MSB
USICR,r17
USICR,r16
USICR,r17
USICR,r16
USICR,r17
USICR,r16
USICR,r17
USICR,r16
USICR,r17
USICR,r16
USICR,r17
USICR,r16
USICR,r17
USICR,r16 ; LSB
USICR,r17
r16,USIDR
r16,(1<<USIWM0)|(1<<USICS1)
USICR,r16
8006G–AVR–01/08