ATMEGA328P-20PU Atmel, ATMEGA328P-20PU Datasheet - Page 226

• Manufacturer Part Number: ATMEGA328P-20PU
• Manufacturer: Atmel

Specifications of ATMEGA328P-20PU

• Cpu Family: ATmega
• Device Core: AVR
• Device Core Size: 8b
• Frequency (max): 20MHz
• Interface Type: SPI/TWI/USART
• Program Memory Type: Flash
• Program Memory Size: 32KB
• Total Internal Ram Size: 2KB
• # I/os (max): 23
• Number Of Timers - General Purpose: 3
• Operating Supply Voltage (typ): 3.3/5V
• Operating Supply Voltage (max): 5.5V
• Operating Supply Voltage (min): 2.7V
• On-chip Adc: 6-chx10-bit
• Instruction Set Architecture: RISC
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Mounting: Through Hole
• Pin Count: 28
• Package Type: PDIP
• Lead Free Status / Rohs Status: Compliant

Table 21-2.
8025K–AVR–10/09
Status Code
(TWSR)
Prescaler Bits
are 0
0x08
0x10
0x18
0x20
0x28
0x30
0x38
Status of the 2-wire Serial Bus
and 2-wire Serial Interface
Hardware
A START condition has been
transmitted
A repeated START condition
has been transmitted
SLA+W has been transmitted;
ACK has been received
SLA+W has been transmitted;
NOT ACK has been received
Data byte has been transmit-
ted;
ACK has been received
Data byte has been transmit-
ted;
NOT ACK has been received
Arbitration lost in SLA+W or
data bytes
Status codes for Master Transmitter Mode
After a repeated START condition (state 0x10) the 2-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 with-
out losing control of the bus.
To/from TWDR
Load SLA+W
Load SLA+W or
Load SLA+R
Load data byte or
No TWDR action or
No TWDR action or
No TWDR action
Load data byte or
No TWDR action or
No TWDR action or
No TWDR action
Load data byte or
No TWDR action or
No TWDR action or
No TWDR action
Load data byte or
No TWDR action or
No TWDR action or
No TWDR action
No TWDR action or
No TWDR action
Application Software Response
STA
0
0
0
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
STO
0
0
0
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
To TWCR
TWIN
T
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
TWE
A
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
ATmega48P/88P/168P
Next Action Taken by TWI Hardware
SLA+W will be transmitted;
ACK or NOT ACK will be received
SLA+W will be transmitted;
ACK or NOT ACK will be received
SLA+R will be transmitted;
Logic will switch to Master Receiver mode
Data byte will be transmitted and ACK or NOT ACK will
be received
Repeated START will be transmitted
STOP condition will be transmitted and
TWSTO Flag will be reset
STOP condition followed by a START condition will be
transmitted and TWSTO Flag will be reset
Data byte will be transmitted and ACK or NOT ACK will
be received
Repeated START will be transmitted
STOP condition will be transmitted and
TWSTO Flag will be reset
STOP condition followed by a START condition will be
transmitted and TWSTO Flag will be reset
Data byte will be transmitted and ACK or NOT ACK will
be received
Repeated START will be transmitted
STOP condition will be transmitted and
TWSTO Flag will be reset
STOP condition followed by a START condition will be
transmitted and TWSTO Flag will be reset
Data byte will be transmitted and ACK or NOT ACK will
be received
Repeated START will be transmitted
STOP condition will be transmitted and
TWSTO Flag will be reset
STOP condition followed by a START condition will be
transmitted and TWSTO Flag will be reset
2-wire Serial Bus will be released and not addressed
Slave mode entered
A START condition will be transmitted when the bus
becomes free
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