ATmega8535 Atmel Corporation, ATmega8535 Datasheet - Page 189

• Manufacturer Part Number: ATmega8535
• Manufacturer: Atmel Corporation

Specifications of ATmega8535

• Flash (kbytes): 8 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): 0.5
• Eeprom (bytes): 512
• 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

Master Transmitter Mode
2502K–AVR–10/06
In the Master Transmitter mode, a number of data bytes are transmitted to a Slave
Receiver (see Figure 86). In order to enter a Master mode, a START condition must be
transmitted. The format of the following address packet determines whether Master
Transmitter or Master Receiver mode is to be entered. If SLA+W is transmitted, MT
mode is entered, if SLA+R is transmitted, MR mode is entered. All the status codes
mentioned in this section assume that the prescaler bits are zero or are masked to zero.
Figure 86. Data Transfer in Master Transmitter Mode
A START condition is sent by writing the following value to TWCR:
TWEN must be set to enable the Two-wire Serial Interface, TWSTA must be written to
one to transmit a START condition and TWINT must be written to one 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 transmit-
ted, the TWINT Flag is set by hardware, and the status code in TWSR will be 0x08 (see
Table 75). In order to enter MT mode, SLA+W must be transmitted. This is done by writ-
ing SLA+W 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+W 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 sta-
tus codes in Master mode are 0x18, 0x20, or 0x38. The appropriate action to be taken
for each of these status codes is detailed in Table 75.
When SLA+W has been successfully transmitted, a data packet should be transmitted.
This is done by writing the data byte to TWDR. TWDR must only be written when
TWINT is high. If not, the access will be discarded, and the Write Collision bit (TWWC)
will be set in the TWCR Register. After updating TWDR, 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:
SDA
SCL
TWCR
Value
TWCR
Value
TWCR
Value
TRANSMITTER
Device 1
MASTER
TWINT
TWINT
TWINT
1
1
1
RECEIVER
Device 2
TWEA
TWEA
TWEA
SLAVE
X
X
X
TWSTA
TWSTA
TWSTA
1
0
0
Device 3
TWSTO
TWSTO
TWSTO
0
0
0
........
TWWC
TWWC
TWWC
X
X
X
Device n
ATmega8535(L)
V
CC
TWEN
TWEN
TWEN
1
1
1
R1
–
0
–
0
–
0
R2
TWIE
TWIE
TWIE
X
X
X
189