ATtiny88 Atmel Corporation, ATtiny88 Datasheet - Page 158

• Manufacturer Part Number: ATtiny88
• Manufacturer: Atmel Corporation

Specifications of ATtiny88

• Flash (kbytes): 8 Kbytes
• Pin Count: 32
• Max. Operating Frequency: 12 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 12
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 28
• Ext Interrupts: 28
• 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): 64
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: Yes
• 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: 2
• 32khz Rtc: No
• Calibrated Rc Oscillator: Yes

15.11.3
158
ATtiny48/88
TWSR – TWI Status Register
• Bit 5 – TWSTA: TWI START Condition Bit
The application writes the TWSTA bit to one when it desires to become a Master on the 2-wire
Serial Bus. The TWI hardware checks if the bus is available, and generates a START condition
on the bus if it is free. However, if the bus is not free, the TWI waits until a STOP condition is
detected, and then generates a new START condition to claim the bus Master status. TWSTA
must be cleared by software when the START condition has been transmitted.
• Bit 4 – TWSTO: TWI STOP Condition Bit
Writing the TWSTO bit to one in Master mode will generate a STOP condition on the 2-wire
Serial Bus. When the STOP condition is executed on the bus, the TWSTO bit is cleared auto-
matically. In Slave mode, setting the TWSTO bit can be used to recover from an error condition.
This will not generate a STOP condition, but the TWI returns to a well-defined unaddressed
Slave mode and releases the SCL and SDA lines to a high impedance state.
• Bit 3 – TWWC: TWI Write Collision Flag
The TWWC bit is set when attempting to write to the TWI Data Register – TWDR when TWINT is
low. This flag is cleared by writing the TWDR Register when TWINT is high.
• Bit 2 – TWEN: TWI Enable Bit
The TWEN bit enables TWI operation and activates the TWI interface. When TWEN is written to
one, the TWI takes control over the I/O pins connected to the SCL and SDA pins, enabling the
slew-rate limiters and spike filters. If this bit is written to zero, the TWI is switched off and all TWI
transmissions are terminated, regardless of any ongoing operation.
• Bit 1 – Res: Reserved Bit
This bit is reserved and will always read as zero.
• Bit 0 – TWIE: TWI Interrupt Enable
When this bit is written to one, and the I-bit in SREG is set, the TWI interrupt request will be acti-
vated for as long as the TWINT Flag is high.
• Bits 7:3 – TWS: TWI Status
These 5 bits reflect the status of the TWI logic and the 2-wire Serial Bus. The different status
codes are described later in this section. Note that the value read from TWSR contains both the
5-bit status value and the 2-bit prescaler value. The application designer should mask the pres-
caler bits to zero when checking the Status bits. This makes status checking independent of
prescaler setting. This approach is used in this datasheet, unless otherwise noted.
• Bit 2 – Res: Reserved Bit
This bit is reserved and will always read as zero.
Bit
(0xB9)
Read/Write
Initial Value
TWS7
R
7
1
TWS6
R
6
1
TWS5
R
5
1
TWS4
R
4
1
TWS3
R
3
1
R
2
–
0
TWPS1
R/W
1
0
TWPS0
R/W
0
0
8008H–AVR–04/11
TWSR