ATMEGA64A-MNR Atmel, ATMEGA64A-MNR Datasheet - Page 222

• Manufacturer Part Number: ATMEGA64A-MNR
• Description: IC MCU AVR 64K FLASH 8QFN
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA64A-MNR

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 16MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 53
• Program Memory Size: 64KB (32K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 2K x 8
• Ram Size: 4K x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: *
• Core: AVR8
• Data Bus Width: 8 bit
• Data Ram Size: 2 KB
• Interface Type: SPI, UART, I2C
• Maximum Clock Frequency: 16 MHz
• Number Of Programmable I/os: 53
• Operating Supply Voltage: 2.7 V to 5.5 V
• Maximum Operating Temperature: + 105 C
• Mounting Style: SMD/SMT
• Operating Temperature Range: - 40 C to + 85 C
• Processor To Be Evaluated: ATMEGA64A
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

8160C–AVR–07/09
Figure 21-17. Data Transfer in Slave Transmitter Mode
To initiate the Slave Transmitter mode, TWAR and TWCR must be initialized as follows:
The upper seven bits are the address to which the Two-wire Serial Interface will respond when
addressed by a master. If the LSB is set, the TWI will respond to the general call address (0x00),
otherwise it will ignore the general call address.
TWEN must be written to one to enable the TWI. The TWEA bit must be written to one to enable
the acknowledgment of the device’s own slave address or the general call address. TWSTA and
TWSTO must be written to zero.
When TWAR and TWCR have been initialized, the TWI waits until it is addressed by its own
slave address (or the general call address if enabled) followed by the data direction bit. If the
direction bit is “1” (read), the TWI will operate in ST mode, otherwise SR mode is entered. After
its own slave address and the write bit have been received, the TWINT flag is set and a valid
status code can be read from TWSR. The status code is used to determine the appropriate soft-
ware action. The appropriate action to be taken for each status code is detailed in
The Slave Transmitter mode may also be entered if arbitration is lost while the TWI is in the
Master mode (see state 0xB0).
If the TWEA bit is written to zero during a transfer, the TWI will transmit the last byte of the trans-
fer. State 0xC0 or state 0xC8 will be entered, depending on whether the master receiver
transmits a NACK or ACK after the final byte. The TWI is switched to the not addressed Slave
mode, and will ignore the master if it continues the transfer. Thus the master receiver receives
all “1” as serial data. State 0xC8 is entered if the master demands additional data bytes (by
transmitting ACK), even though the slave has transmitted the last byte (TWEA zero and expect-
ing NACK from the master).
While TWEA is zero, the TWI does not respond to its own slave address. However, the Two-wire
Serial Bus is still monitored and address recognition may resume at any time by setting TWEA.
This implies that the TWEA bit may be used to temporarily isolate the TWI from the Two-wire
Serial Bus.
TWAR
TWCR
Value
Value
SDA
SCL
TRANSMITTER
Device 1
SLAVE
TWINT
TWA6
0
Device 2
RECEIVER
MASTER
TWEA
TWA5
1
TWSTA
TWA4
Device 3
0
Device’s Own Slave Address
TWSTO
TWA3
0
........
TWWC
TWA2
Device n
0
V
CC
TWEN
TWA1
1
ATmega64A
R1
TWA0
–
0
R2
Table
TWGCE
TWIE
X
21-5.
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