ATTINY44-20MU Atmel, ATTINY44-20MU Datasheet - Page 120

• Manufacturer Part Number: ATTINY44-20MU
• Description: IC MCU AVR 4K FLASH 20MHZ 20-QFN
• Manufacturer: Atmel
• Series: AVR® ATtinyr

Specifications of ATTINY44-20MU

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: USI
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 12
• Program Memory Size: 4KB (2K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 256 x 8
• Ram Size: 256 x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 20-MLF®, QFN
• Data Bus Width: 8 bit
• Data Ram Size: 256 B
• Interface Type: SPI
• Maximum Clock Frequency: 20 MHz
• Number Of Programmable I/os: 12
• Number Of Timers: 2
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• On-chip Adc: 10 bit, 8 Channel
• For Use With: ATAVRISP2 - PROGRAMMER AVR IN SYSTEM
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

120
ATtiny24/44/84
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
SCK
SPITransfer_loop:
SPITransfer_Fast:
ret
= f
CK
out
in
sbrs
rjmp
in
ret
out
ldi
ldi
out
out
out
out
out
out
out
out
out
out
out
out
out
out
out
out
in
/2):
USICR,r17
r16, USISR
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
8006K–AVR–10/10