ATmega32A Atmel Corporation, ATmega32A Datasheet - Page 187

• Manufacturer Part Number: ATmega32A
• Manufacturer: Atmel Corporation

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

20.7
8155C–AVR–02/11
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Assembly code example
ldi
out
wait1:
in
sbrs r16,TWINT
rjmp wait1
in
andi r16, 0xF8
cpi
brne ERROR
ldi
out
ldi
out
wait2:
in
sbrs r16,TWINT
rjmp wait2
in
andi r16, 0xF8
cpi
brne ERROR
ldi
out
ldi
out
wait3:
in
sbrs r16,TWINT
rjmp wait3
in
andi r16, 0xF8
cpi
brne ERROR
ldi
out
Transmission Modes
r16, (1<<TWINT)|(1<<TWSTA)|
(1<<TWEN)
TWCR, r16
r16,TWCR
r16,TWSR
r16, START
r16, SLA_W
TWDR, r16
r16, (1<<TWINT) | (1<<TWEN)
TWCR, r16
r16,TWCR
r16,TWSR
r16, MT_SLA_ACK
r16, DATA
TWDR, r16
r16, (1<<TWINT) | (1<<TWEN)
TWCR, r16
r16,TWCR
r16,TWSR
r16, MT_DATA_ACK
r16, (1<<TWINT)|(1<<TWEN)|
(1<<TWSTO)
TWCR, r16
The TWI can operate in one of four major modes. These are named Master Transmitter (MT),
Master Receiver (MR), Slave Transmitter (ST) and Slave Receiver (SR). Several of these
modes can be used in the same application. As an example, the TWI can use MT mode to write
data into a TWI EEPROM, MR mode to read the data back from the EEPROM. If other masters
are present in the system, some of these might transmit data to the TWI, and then SR mode
would be used. It is the application software that decides which modes are legal.
C example
TWCR = (1<<TWINT)|(1<<TWSTA)|
while (!(TWCR & (1<<TWINT)))
if ((TWSR & 0xF8) != START)
TWDR = SLA_W;
TWCR = (1<<TWINT) | (1<<TWEN);
while (!(TWCR & (1<<TWINT)))
if ((TWSR & 0xF8) != MT_SLA_ACK)
TWDR = DATA;
TWCR = (1<<TWINT) | (1<<TWEN);
while (!(TWCR & (1<<TWINT)))
if ((TWSR & 0xF8) != MT_DATA_ACK)
TWCR = (1<<TWINT)|(1<<TWEN)|
(1<<TWEN)
(1<<TWSTO);
;
ERROR();
;
ERROR();
;
ERROR();
Comments
Send START condition
Wait for TWINT Flag set. This indicates
that the START condition has been
transmitted
Check value of TWI Status Register. Mask
prescaler bits. If status different from
START go to ERROR
Load SLA_W into TWDR Register. Clear
TWINT bit in TWCR to start transmission
of address
Wait for TWINT Flag set. This indicates
that the SLA+W has been transmitted,
and ACK/NACK has been received.
Check value of TWI Status Register. Mask
prescaler bits. If status different from
MT_SLA_ACK go to ERROR
Load DATA into TWDR Register. Clear
TWINT bit in TWCR to start transmission
of data
Wait for TWINT Flag set. This indicates
that the DATA has been transmitted, and
ACK/NACK has been received.
Check value of TWI Status Register. Mask
prescaler bits. If status different from
MT_DATA_ACK go to ERROR
Transmit STOP condition
ATmega32A
187