ATmega32A Atmel Corporation, ATmega32A Datasheet - Page 204

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ATmega32A

Manufacturer Part Number
ATmega32A
Description
Manufacturer
Atmel Corporation
Datasheets

Specifications of ATmega32A

Flash (kbytes)
32 Kbytes
Pin Count
44
Max. Operating Frequency
16 MHz
Cpu
8-bit AVR
# Of Touch Channels
16
Hardware Qtouch Acquisition
No
Max I/o Pins
32
Ext Interrupts
3
Usb Speed
No
Usb Interface
No
Spi
1
Twi (i2c)
1
Uart
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
No
Crypto Engine
No
Sram (kbytes)
2
Eeprom (bytes)
1024
Self Program Memory
YES
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
3
Output Compare Channels
4
Input Capture Channels
1
Pwm Channels
4
32khz Rtc
Yes
Calibrated Rc Oscillator
Yes

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20.9.3
20.9.4
8155C–AVR–02/11
TWSR – TWI Status Register
TWDR – TWI Data Register
• 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 – Reserved Bit
This bit is a reserved bit 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 five bits reflect the status of the TWI logic and the Two-wire Serial Bus. The different sta-
tus 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
prescaler 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 – Reserved Bit
This bit is reserved and will always read as zero.
• Bits 1:0 – TWPS: TWI Prescaler Bits
These bits can be read and written, and control the bit rate prescaler.
Table 20-7.
To calculate bit rates, see
in the equation.
Bit
Read/Write
Initial Value
Bit
Read/Write
Initial Value
TWPS1
0
0
1
1
TWI Bit Rate Prescaler
TWD7
TWS7
R/W
R
7
1
7
1
TWD6
TWS6
R/W
“Bit Rate Generator Unit” on page
R
6
1
6
1
TWD5
TWS5
TWPS0
R/W
R
5
1
5
1
0
1
0
1
TWD4
TWS4
R/W
R
4
1
4
1
Prescaler Value
1
4
16
64
TWD3
TWS3
R/W
R
3
1
3
1
182. The value of TWPS1:0 is used
TWD2
R/W
R
2
0
2
1
TWPS1
TWD1
R/W
R/W
1
1
1
0
ATmega32A
TWPS0
TWD0
R/W
R/W
0
1
0
0
TWDR
TWSR
204

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