ATmega32 Atmel Corporation, ATmega32 Datasheet - Page 187

• Manufacturer Part Number: ATmega32
• Manufacturer: Atmel Corporation

Specifications of ATmega32

• 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

Table 75. Status Codes for Master Receiver Mode
2503Q–AVR–02/11
Status Code
(TWSR)
Prescaler Bits
are 0
Status of the Two-wire Serial
Bus and Two-wire Serial Inter-
face Hardware
Figure 88. Data Transfer in Master Receiver Mode
A START condition is sent by writing the following value to TWCR:
TWEN must be written to one to enable the Two-wire Serial Interface, TWSTA must be written to
one to transmit a START condition and TWINT must be set to clear the TWINT Flag. The TWI
will then test the Two-wire Serial Bus and generate a START condition as soon as the bus
becomes free. After a START condition has been transmitted, the TWINT Flag is set by hard-
ware, and the status code in TWSR will be $08 (See
SLA+R must be transmitted. This is done by writing SLA+R to TWDR. Thereafter the TWINT bit
should be cleared (by writing it to one) to continue the transfer. This is accomplished by writing
the following value to TWCR:
When SLA+R have been transmitted and an acknowledgement bit has been received, TWINT is
set again and a number of status codes in TWSR are possible. Possible status codes in master
mode are $38, $40, or $48. The appropriate action to be taken for each of these status codes is
detailed in
is set high by hardware. This scheme is repeated until the last byte has been received. After the
last byte has been received, the MR should inform the ST by sending a NACK after the last
received data byte. The transfer is ended by generating a STOP condition or a repeated START
condition. A STOP condition is generated by writing the following value to TWCR:
A REPEATED START condition is generated by writing the following value to TWCR:
After a repeated START condition (state $10) the Two-wire Serial Interface can access the
same slave again, or a new slave without transmitting a STOP condition. Repeated START
enables the master to switch between slaves, Master Transmitter mode and Master Receiver
mode without losing control over the bus.
TWCR
Value
TWCR
Value
TWCR
Value
TWCR
Value
SDA
SCL
Table
To/from TWDR
TWINT
TWINT
TWINT
TWINT
1
1
1
1
75. Received data can be read from the TWDR Register when the TWINT Flag
Device 1
RECEIVER
MASTER
Application Software Response
TWEA
TWEA
TWEA
TWEA
X
X
X
X
STA
TRANSMITTER
Device 2
TWSTA
TWSTA
TWSTA
TWSTA
SLAVE
1
0
0
1
STO
To TWCR
TWSTO
TWSTO
TWSTO
TWSTO
TWINT
Device 3
0
0
1
0
TWEA
TWWC
TWWC
TWWC
TWWC
X
X
X
X
........
Table
Next Action Taken by TWI Hardware
TWEN
TWEN
TWEN
TWEN
74). In order to enter MR mode,
Device n
1
1
1
1
V
CC
ATmega32(L)
–
0
–
0
–
0
–
0
R1
TWIE
TWIE
TWIE
TWIE
R2
X
X
X
X
187