ATMEGA324P-A15MZ Atmel, ATMEGA324P-A15MZ Datasheet - Page 177

• Manufacturer Part Number: ATMEGA324P-A15MZ
• Description: MCU AVR 32KB FLASH 15MHZ 44-VQFN
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA324P-A15MZ

• Package / Case: 44-VQFN Exposed Pad
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Operating Temperature: -40°C ~ 125°C
• Speed: 16MHz
• Number Of I /o: 32
• Eeprom Size: 1K x 8
• Core Processor: AVR
• Program Memory Type: FLASH
• Ram Size: 2K x 8
• Program Memory Size: 32KB (32K x 8)
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Connectivity: I²C, SPI, UART/USART
• Core Size: 8-Bit
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

TWI Register
Description
TWI Bit Rate Register
– TWBR
TWI Control Register –
TWCR
2503N–AVR–06/08
• Bits 7..0 – TWI Bit Rate Register
TWBR selects the division factor for the bit rate generator. The bit rate generator is a frequency
divider which generates the SCL clock frequency in the Master modes. See
Unit” on page 175
The TWCR is used to control the operation of the TWI. It is used to enable the TWI, to initiate a
master access by applying a START condition to the bus, to generate a receiver acknowledge,
to generate a stop condition, and to control halting of the bus while the data to be written to the
bus are written to the TWDR. It also indicates a write collision if data is attempted written to
TWDR while the register is inaccessible.
• Bit 7 – TWINT: TWI Interrupt Flag
This bit is set by hardware when the TWI has finished its current job and expects application
software response. If the I-bit in SREG and TWIE in TWCR are set, the MCU will jump to the
TWI Interrupt Vector. While the TWINT Flag is set, the SCL low period is stretched.
The TWINT Flag must be cleared by software by writing a logic one to it. Note that this flag is not
automatically cleared by hardware when executing the interrupt routine. Also note that clearing
this flag starts the operation of the TWI, so all accesses to the TWI Address Register (TWAR),
TWI Status Register (TWSR), and TWI Data Register (TWDR) must be complete before clearing
this flag.
• Bit 6 – TWEA: TWI Enable Acknowledge Bit
The TWEA bit controls the generation of the acknowledge pulse. If the TWEA bit is written to
one, the ACK pulse is generated on the TWI bus if the following conditions are met:
1. The device’s own slave address has been received.
2. A general call has been received, while the TWGCE bit in the TWAR is set.
3. A data byte has been received in Master Receiver or Slave Receiver mode.
By writing the TWEA bit to zero, the device can be virtually disconnected from the Two-wire
Serial Bus temporarily. Address recognition can then be resumed by writing the TWEA bit to one
again.
• Bit 5 – TWSTA: TWI START Condition Bit
The application writes the TWSTA bit to one when it desires to become a master on the Two-
wire Serial Bus. The TWI hardware checks if the bus is available, and generates a START con-
dition on the bus if it is free. However, if the bus is not free, the TWI waits until a STOP condition
Bit
Read/Write
Initial Value
Bit
Read/Write
Initial Value
TWBR7
TWINT
R/W
R/W
7
0
7
0
for calculating bit rates.
TWBR6
TWEA
R/W
R/W
6
0
6
0
TWBR5
TWSTA
R/W
R/W
5
0
5
0
TWBR4
TWSTO
R/W
R/W
4
0
4
0
TWBR3
TWWC
R/W
R
3
0
3
0
TWBR2
TWEN
R/W
R/W
2
0
2
0
TWBR1
R/W
R
1
0
1
–
0
ATmega32(L)
TWBR0
TWIE
R/W
R/W
0
0
0
0
“Bit Rate Generator
TWBR
TWCR
177