ATTINY85-15ST1 Atmel, ATTINY85-15ST1 Datasheet - Page 100

• Manufacturer Part Number: ATTINY85-15ST1
• Description: MCU AVR 8K FLASH 15MHZ 8-SOIC
• Manufacturer: Atmel
• Series: AVR® ATtinyr

Specifications of ATTINY85-15ST1

• Package / Case: 8-SOIC (3.9mm Width)
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Operating Temperature: -40°C ~ 105°C
• Speed: 16MHz
• Number Of I /o: 6
• Eeprom Size: 512 x 8
• Core Processor: AVR
• Program Memory Type: FLASH
• Ram Size: 512 x 8
• Program Memory Size: 8KB (8K x 8)
• Data Converters: A/D 4x10b
• Oscillator Type: Internal
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Connectivity: USI
• Core Size: 8-Bit
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

16.2.3
16.2.4
100
ATtiny25/45/85
SPI Slave Operation Example
Two-wire Mode
The following code demonstrates how to use the USI module as a SPI Slave:
The code is size optimized using only eight instructions (+ ret). The code example assumes that
the DO is configured as output and USCK pin is configured as input in the DDR Register. The
value stored in register r16 prior to the function is called is transferred to the master device, and
when the transfer is completed the data received from the Master is stored back into the r16
Register.
Note that the first two instructions is for initialization only and needs only to be executed
once.These instructions sets Three-wire mode and positive edge Shift Register clock. The loop
is repeated until the USI Counter Overflow Flag is set.
The USI Two-wire mode is compliant to the Inter IC (TWI) bus protocol, but without slew rate lim-
iting on outputs and input noise filtering. Pin names used by this mode are SCL and SDA.
init:
...
SlaveSPITransfer:
SlaveSPITransfer_loop:
ldi
sts
sts
ldi
sts
lds
sbrs
rjmp
lds
ret
r16,(1<<USIWM0)|(1<<USICS1)
USICR,r16
USIDR,r16
r16,(1<<USIOIF)
USISR,r16
r16, USISR
r16, USIOIF
SlaveSPITransfer_loop
r16,USIDR
7598H–AVR–07/09