ATtiny26 Atmel Corporation, ATtiny26 Datasheet - Page 89

• Manufacturer Part Number: ATtiny26
• Manufacturer: Atmel Corporation

Specifications of ATtiny26

• Flash (kbytes): 2 Kbytes
• Pin Count: 20
• Max. Operating Frequency: 16 MHz
• Cpu: 8-bit AVR
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 16
• Ext Interrupts: 11
• Usb Speed: No
• Usb Interface: No
• Spi: 1
• Twi (i2c): 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 11
• Adc Resolution (bits): 10
• Adc Speed (ksps): 15
• Analog Comparators: 1
• Resistive Touch Screen: No
• Temp. Sensor: No
• Crypto Engine: No
• Sram (kbytes): 0.12
• Eeprom (bytes): 128
• Self Program Memory: NO
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 2.7 to 5.5
• Operating Voltage (vcc): 2.7 to 5.5
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 2
• Output Compare Channels: 3
• Pwm Channels: 4
• 32khz Rtc: No
• Calibrated Rc Oscillator: Yes

1477K–AVR–08/10
Figure 48. Two-wire Mode, Typical Timing Diagram
Referring to the timing diagram (Figure 48.), a bus transfer involves the following steps:
1. The a start condition is generated by the master by forcing the SDA low line while the
2. In addition, the start detector will hold the SCL line low after the master has forced an
3. The master set the first bit to be transferred and releases the SCL line (C). The slave
4. After eight bits are transferred containing slave address and data direction (read or
5. If the slave is addressed it holds the SDA line low during the acknowledgment cycle
6. Multiple bytes can now be transmitted, all in same direction, until a stop condition is given
If the slave is not able to receive more data it does not acknowledge the data byte it has last
received. When the master does a read operation it must terminate the operation by force the
acknowledge bit low after the last byte transmitted.
Figure 49. Start Condition Detector, Logic Diagram
SCL line is high (A). SDA can be forced low either by writing a zero to bit 7 of the Shift
Register, or by setting the PORTB0 bit to zero. Note that DDRB0 must be set to one for
the output to be enabled. The slave device’s start detector logic (Figure 49.) detects the
start condition and sets the USISIF flag. The flag can generate an interrupt if necessary.
negative edge on this line (B). This allows the slave to wake up from sleep or complete
its other tasks, before setting up the Shift Register to receive the address by clearing the
start condition flag and reset the counter.
samples the data and shift it into the serial register at the positive edge of the SCL clock.
write), the slave counter overflows and the SCL line is forced low (D). If the slave is not
the one the master has addressed it releases the SCL line and waits for a new start
condition.
before holding the SCL line low again (i.e., the Counter Register must be set to 14 before
releasing SCL at (D)). Depending of the R/W bit the master or slave enables its output. If
the bit is set, a master read operation is in progress (i.e., the slave drives the SDA line)
The slave can hold the SCL line low after the acknowledge (E).
by the master (F). Or a new start condition is given.
SDA
SCL
Write( USISIF)
A B
S
C
ADDRESS
SDA
SCL
1 - 7
R/W
8
D
ACK
9
E
DATA
1 - 8
D Q
CLR
ACK
9
D Q
CLR
DATA
1 - 8
USISIF
CLOCK
HOLD
ACK
9
P
F
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