ATMEGA644PV ATMEL [ATMEL Corporation], ATMEGA644PV Datasheet - Page 171
ATMEGA644PV
Manufacturer Part Number
ATMEGA644PV
Description
8-bit Microcontroller with 16/32/64K Bytes In-System Programmable Flash
Manufacturer
ATMEL [ATMEL Corporation]
Datasheet
1.ATMEGA644PV.pdf
(408 pages)
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Part Number:
ATMEGA644PV-10MU
Manufacturer:
ATMEL/爱特梅尔
Quantity:
20 000
- Current page: 171 of 408
- Download datasheet (4Mb)
17.4.1
8011D–AVR–02/07
Internal Clock Generation – The Baud Rate Generator
UCSRnA Register. When using synchronous mode (UMSELn = 1), the Data Direction Register
for the XCKn pin (DDR_XCKn) controls whether the clock source is internal (Master mode) or
external (Slave mode). The XCKn pin is only active when using synchronous mode.
Figure 17-2
Figure 17-2. Clock Generation Logic, Block Diagram
Signal description:
operation.
Internal clock generation is used for the asynchronous and the synchronous master modes of
operation. The description in this section refers to
The USART Baud Rate Register (UBRRn) and the down-counter connected to it function as a
programmable prescaler or baud rate generator. The down-counter, running at system clock
(f
the UBRRLn Register is written. A clock is generated each time the counter reaches zero. This
clock is the baud rate generator clock output (= f
baud rate generator clock output by 2, 8 or 16 depending on mode. The baud rate generator out-
put is used directly by the Receiver’s clock and data recovery units. However, the recovery units
use a state machine that uses 2, 8 or 16 states depending on mode set by the state of the
UMSELn, U2Xn and DDR_XCKn bits.
Table 17-1 on page 172
for calculating the UBRRn value for each mode of operation using an internally generated clock
source.
Note:
osc
), is loaded with the UBRRn value each time the counter has counted down to zero or when
txclk
rxclk
xcki
xcko
f
BAUD
OSC
DDR_XCK
1. The baud rate is defined to be the transfer rate in bit per second (bps)
XCK
Pin
shows a block diagram of the clock generation logic.
xcko
xcki
OSC
Transmitter clock (Internal Signal).
Receiver base clock (Internal Signal).
Input from XCK pin (internal Signal). Used for synchronous slave
Clock output to XCK pin (Internal Signal). Used for synchronous master
operation.
XTAL pin frequency (System Clock).
Baud rate (in bits per second, bps)
Down-Counter
Prescaling
contains equations for calculating the baud rate (in bits per second) and
Register
UBRR
Sync
UBRR+1
fosc
Detector
UCPOL
Edge
/2
ATmega164P/324P/644P
Figure 17-2 on page
osc
/(UBRRn+1)). The Transmitter divides the
/4
/2
DDR_XCK
171.
U2X
0
1
0
1
0
1
1
0
UMSEL
txclk
rxclk
171
Related parts for ATMEGA644PV
Image
Part Number
Description
Manufacturer
Datasheet
Request
R
Part Number:
Description:
Atmel CryptoMemory
Manufacturer:
ATMEL [ATMEL Corporation]
Datasheet:
Part Number:
Description:
Atmel CryptoMemory
Manufacturer:
ATMEL [ATMEL Corporation]
Datasheet:
Part Number:
Description:
Atmel CryptoMemory, 16Kbit
Manufacturer:
ATMEL [ATMEL Corporation]
Datasheet:
Part Number:
Description:
8-bit Atmel Microcontrollers
Manufacturer:
ATMEL [ATMEL Corporation]
Datasheet:
Part Number:
Description:
8-bit Atmel Microcontroller with 64K/128K/256K Bytes In-System Programmable Flash
Manufacturer:
ATMEL [ATMEL Corporation]
Datasheet:
Part Number:
Description:
8-bit Atmel Microcontroller with 16/32/64/128K Bytes In-System Programmable Flash
Manufacturer:
ATMEL [ATMEL Corporation]
Datasheet:
Part Number:
Description:
8-bit Atmel Microcontroller with 16/32/64K Bytes In-System Programmable Programmable
Manufacturer:
ATMEL [ATMEL Corporation]
Datasheet:
Part Number:
Description:
INTERVAL AND WIPE/WASH WIPER CONTROL IC WITH DELAY
Manufacturer:
ATMEL Corporation
Datasheet:
Part Number:
Description:
Low-Voltage Voice-Switched IC for Hands-Free Operation
Manufacturer:
ATMEL Corporation
Datasheet:
Part Number:
Description:
MONOLITHIC INTEGRATED FEATUREPHONE CIRCUIT
Manufacturer:
ATMEL Corporation
Datasheet:
Part Number:
Description:
AM-FM Receiver IC U4255BM-M
Manufacturer:
ATMEL Corporation
Datasheet:
Part Number:
Description:
Monolithic Integrated Feature Phone Circuit
Manufacturer:
ATMEL Corporation
Datasheet:
Part Number:
Description:
Multistandard Video-IF and Quasi Parallel Sound Processing
Manufacturer:
ATMEL Corporation
Datasheet: