ATMEGA164P-20AQ Atmel, ATMEGA164P-20AQ Datasheet - Page 213

• Manufacturer Part Number: ATMEGA164P-20AQ
• Description: MCU AVR 16K FLASH 20MHZ 44-TQFP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA164P-20AQ

• 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: 32
• Program Memory Size: 16KB (8K 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: 44-TQFP, 44-VQFP
• For Use With: ATSTK600-TQFP44 - STK600 SOCKET/ADAPTER 44-TQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

18.5
18.5.1
18.5.2
8011O–AVR–07/10
Overview of the TWI Module
SCL and SDA Pins
Bit Rate Generator Unit
The TWI module is comprised of several submodules, as shown in
drawn in a thick line are accessible through the AVR data bus.
Figure 18-9. Overview of the TWI Module
These pins interface the AVR TWI with the rest of the MCU system. The output drivers contain a
slew-rate limiter in order to conform to the TWI specification. The input stages contain a spike
suppression unit removing spikes shorter than 50 ns. Note that the internal pull-ups in the AVR
pads can be enabled by setting the PORT bits corresponding to the SCL and SDA pins, as
explained in the I/O Port section. The internal pull-ups can in some systems eliminate the need
for external ones.
This unit controls the period of SCL when operating in a Master mode. The SCL period is con-
trolled by settings in the TWI Bit Rate Register (TWBR) and the Prescaler bits in the TWI Status
Register (TWSR). Slave operation does not depend on Bit Rate or Prescaler settings, but the
CPU clock frequency in the Slave must be at least 16 times higher than the SCL frequency. Note
that slaves may prolong the SCL low period, thereby reducing the average TWI bus clock
period. The SCL frequency is generated according to the following equation:
Slew-rate
Address Match Unit
Arbitration detection
Control
START / STOP
Address Comparator
Address Register
Control
SCL
(TWAR)
Spike
Filter
Bus Interface Unit
Address/Data Shift
Spike Suppression
Register (TWDR)
Slew-rate
Control
SDA
Status Register
ATmega164P/324P/644P
Ack
Spike
Filter
(TWSR)
State Machine and
Control Unit
Status control
Bit Rate Generator
Control Register
Bit Rate Register
Figure
Prescaler
(TWCR)
(TWBR)
18-9. All registers
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