ATtiny84 Atmel Corporation, ATtiny84 Datasheet - Page 127

• Manufacturer Part Number: ATtiny84
• Manufacturer: Atmel Corporation

Specifications of ATtiny84

• Flash (kbytes): 8 Kbytes
• Pin Count: 14
• Max. Operating Frequency: 20 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 6
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 12
• Ext Interrupts: 12
• Usb Speed: No
• Usb Interface: No
• Spi: 1
• Twi (i2c): 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 8
• Adc Resolution (bits): 10
• Adc Speed (ksps): 15
• Analog Comparators: 1
• Resistive Touch Screen: No
• Temp. Sensor: Yes
• Crypto Engine: No
• Sram (kbytes): 0.5
• Eeprom (bytes): 512
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 1.8 to 5.5
• Operating Voltage (vcc): 1.8 to 5.5
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 2
• Output Compare Channels: 4
• Input Capture Channels: 1
• Pwm Channels: 4
• 32khz Rtc: No
• Calibrated Rc Oscillator: Yes

8006K–AVR–10/10
Table 14-1.
Note:
• Bits 3:2 – USICS1, USICS0: Clock Source Select
These bits set the clock source for the USI Data Register and counter. The data output latch
ensures that the output is changed at the opposite edge of the sampling of the data input
(DI/SDA) when using external clock source (USCK/SCL). When software strobe or
Timer/Counter0 Compare Match clock option is selected, the output latch is transparent and
therefore the output is changed immediately.
Clearing the USICS1:0 bits enables software strobe option. When using this option, writing a
one to the USICLK bit clocks both the USI Data Register and the counter. For external clock
source (USICS1 = 1), the USICLK bit is no longer used as a strobe, but selects between external
clocking and software clocking by the USITC strobe bit.
USIWM1
0
0
1
1
1. The DI and USCK pins are renamed to Serial Data (SDA) and Serial Clock (SCL) respectively
to avoid confusion between the modes of operation.
USIWM0
Relationship between USIWM1:0 and USI Operation
0
1
0
1
Description
Outputs, clock hold, and start detector disabled.
Port pins operate as normal.
Three-wire mode. Uses DO, DI, and USCK pins.
The Data Output (DO) pin overrides the corresponding bit in the PORTA
register. However, the corresponding DDRA bit still controls the data direction.
When the port pin is set as input the pin pull-up is controlled by the PORTA bit.
The Data Input (DI) and Serial Clock (USCK) pins do not affect the normal port
operation. When operating as master, clock pulses are software generated by
toggling the PORTA register, while the data direction is set to output. The
USITC bit in the USICR Register can be used for this purpose.
Two-wire mode. Uses SDA (DI) and SCL (USCK) pins
The Serial Data (SDA) and the Serial Clock (SCL) pins are bi-directional and
use open-collector output drives. The output drivers are enabled by setting the
corresponding bit for SDA and SCL in the DDRA register.
When the output driver is enabled for the SDA pin, the output driver will force the
line SDA low if the output of the
the PORTA register is zero. Otherwise, the SDA line will not be driven (i.e., it is
released). When the SCL pin output driver is enabled the SCL line will be forced
low if the corresponding bit in the PORTA register is zero, or by the start
detector. Otherwise the SCL line will not be driven.
The SCL line is held low when a start detector detects a start condition and the
output is enabled. Clearing the Start Condition Flag (USISIF) releases the line.
The SDA and SCL pin inputs is not affected by enabling this mode. Pull-ups on
the SDA and SCL port pin are disabled in Two-wire mode.
Two-wire mode. Uses SDA and SCL pins.
Same operation as in two-wire mode above, except that the SCL line is also
held low when a counter overflow occurs, and until the Counter Overflow Flag
(USIOIF) is cleared.
USI Data Register
ATtiny24/44/84
or the corresponding bit in
(1)
.
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