ATMEGA88P-20MUR Atmel, ATMEGA88P-20MUR Datasheet - Page 222

• Manufacturer Part Number: ATMEGA88P-20MUR
• Description: MCU AVR 8KB FLASH 20MHZ 32QFN
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA88P-20MUR

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 23
• Program Memory Size: 8KB (4K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 512 x 8
• Ram Size: 1K 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: *
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Figure 21-10. Interfacing the Application to the TWI in a Typical Transmission
8025L–AVR–7/10
writes to TWCR to
TWI bus
transmission of
1. Application
START condition sent
Status code indicates
START
initiate
2. TWINT set.
START
TWDR, and loads appropriate control
3. Check TWSR to see if START was
signals into TWCR, makin sure that
sent. Application loads SLA+W into
1. The first step in a TWI transmission is to transmit a START condition. This is done by
2. When the START condition has been transmitted, the TWINT Flag in TWCR is set, and
3. The application software should now examine the value of TWSR, to make sure that the
4. When the address packet has been transmitted, the TWINT Flag in TWCR is set, and
5. The application software should now examine the value of TWSR, to make sure that the
and TWSTA is written to zero.
TWINT is written to one,
writing a specific value into TWCR, instructing the TWI hardware to transmit a START
condition. Which value to write is described later on. However, it is important that the
TWINT bit is set in the value written. Writing a one to TWINT clears the flag. The TWI will
not start any operation as long as the TWINT bit in TWCR is set. Immediately after the
application has cleared TWINT, the TWI will initiate transmission of the START condition.
TWSR is updated with a status code indicating that the START condition has success-
fully been sent.
START condition was successfully transmitted. If TWSR indicates otherwise, the applica-
tion software might take some special action, like calling an error routine. Assuming that
the status code is as expected, the application must load SLA+W into TWDR. Remember
that TWDR is used both for address and data. After TWDR has been loaded with the
desired SLA+W, a specific value must be written to TWCR, instructing the TWI hardware
to transmit the SLA+W present in TWDR. Which value to write is described later on.
However, it is important that the TWINT bit is set in the value written. Writing a one to
TWINT clears the flag. The TWI will not start any operation as long as the TWINT bit in
TWCR is set. Immediately after the application has cleared TWINT, the TWI will initiate
transmission of the address packet.
TWSR is updated with a status code indicating that the address packet has successfully
been sent. The status code will also reflect whether a Slave acknowledged the packet or
not.
address packet was successfully transmitted, and that the value of the ACK bit was as
expected. If TWSR indicates otherwise, the application software might take some special
action, like calling an error routine. Assuming that the status code is as expected, the
application must load a data packet into TWDR. Subsequently, a specific value must be
written to TWCR, instructing the TWI hardware to transmit the data packet present in
TWDR. Which value to write is described later on. However, it is important that the
TWINT bit is set in the value written. Writing a one to TWINT clears the flag. The TWI will
SLA+W
Status code indicates
SLA+W sent, ACK
4. TWINT set.
received
A
Application loads data into TWDR, and
5. Check TWSR to see if SLA+W was
loads appropriate control signals into
TWCR, making sure that TWINT is
sent and ACK received.
written to one
Data
data sent, ACK received
Status code indicates
6. TWINT set.
ATmega48P/88P/168P
A
making sure that TWINT is written to one
7. Check TWSR to see if data was sent
Application loads appropriate control
signals to send STOP into TWCR,
STOP
and ACK received.
TWINT set
Indicates
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