ATMEGA640V-8CU Atmel, ATMEGA640V-8CU Datasheet - Page 146
![IC MCU AVR 64K FLASH 100-CBGA](/photos/6/89/68968/313-100-cbga_sml.jpg)
ATMEGA640V-8CU
Manufacturer Part Number
ATMEGA640V-8CU
Description
IC MCU AVR 64K FLASH 100-CBGA
Manufacturer
Atmel
Series
AVR® ATmegar
Specifications of ATMEGA640V-8CU
Core Processor
AVR
Core Size
8-Bit
Speed
8MHz
Connectivity
EBI/EMI, I²C, SPI, UART/USART
Peripherals
Brown-out Detect/Reset, POR, PWM, WDT
Number Of I /o
86
Program Memory Size
64KB (32K x 16)
Program Memory Type
FLASH
Eeprom Size
4K x 8
Ram Size
8K x 8
Voltage - Supply (vcc/vdd)
1.8 V ~ 5.5 V
Data Converters
A/D 16x10b
Oscillator Type
Internal
Operating Temperature
-40°C ~ 85°C
Package / Case
100-TFBGA
Processor Series
ATMEGA64x
Core
AVR8
Data Bus Width
8 bit
Data Ram Size
8 KB
Interface Type
2-Wire, SPI, USART
Maximum Clock Frequency
8 MHz
Number Of Programmable I/os
86
Number Of Timers
6
Maximum Operating Temperature
+ 85 C
Mounting Style
SMD/SMT
Minimum Operating Temperature
- 40 C
On-chip Adc
10 bit, 16 Channel
For Use With
ATSTK600-TQFP100 - STK600 SOCKET/ADAPTER 100-TQFP770-1007 - ISP 4PORT ATMEL AVR MCU SPI/JTAGATAVRISP2 - PROGRAMMER AVR IN SYSTEMATSTK503 - STARTER KIT AVR EXP MODULE 100P
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
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16.7.1
16.7.2
16.7.3
2549M–AVR–09/10
Force Output Compare
Compare Match Blocking by TCNTn Write
Using the Output Compare Unit
The OCRnx Register is double buffered when using any of the twelve Pulse Width Modulation
(PWM) modes. For the Normal and Clear Timer on Compare (CTC) modes of operation, the
double buffering is disabled. The double buffering synchronizes the update of the OCRnx Com-
pare Register to either TOP or BOTTOM of the counting sequence. The synchronization
prevents the occurrence of odd-length, non-symmetrical PWM pulses, thereby making the out-
put glitch-free.
The OCRnx Register access may seem complex, but this is not case. When the double buffering
is enabled, the CPU has access to the OCRnx Buffer Register, and if double buffering is dis-
abled the CPU will access the OCRnx directly. The content of the OCR1x (Buffer or Compare)
Register is only changed by a write operation (the Timer/Counter does not update this register
automatically as the TCNT1 and ICR1 Register). Therefore OCR1x is not read via the high byte
temporary register (TEMP). However, it is a good practice to read the low byte first as when
accessing other 16-bit registers. Writing the OCRnx Registers must be done via the TEMP Reg-
ister since the compare of all 16 bits is done continuously. The high byte (OCRnxH) has to be
written first. When the high byte I/O location is written by the CPU, the TEMP Register will be
updated by the value written. Then when the low byte (OCRnxL) is written to the lower eight bits,
the high byte will be copied into the upper 8-bits of either the OCRnx buffer or OCRnx Compare
Register in the same system clock cycle.
For more information of how to access the 16-bit registers refer to
on page
In non-PWM Waveform Generation modes, the match output of the comparator can be forced by
writing a one to the Force Output Compare (FOCnx) bit. Forcing compare match will not set the
OCFnx Flag or reload/clear the timer, but the OCnx pin will be updated as if a real compare
match had occurred (the COMn1:0 bits settings define whether the OCnx pin is set, cleared or
toggled).
All CPU writes to the TCNTn Register will block any compare match that occurs in the next timer
clock cycle, even when the timer is stopped. This feature allows OCRnx to be initialized to the
same value as TCNTn without triggering an interrupt when the Timer/Counter clock is enabled.
Since writing TCNTn in any mode of operation will block all compare matches for one timer clock
cycle, there are risks involved when changing TCNTn when using any of the Output Compare
channels, independent of whether the Timer/Counter is running or not. If the value written to
TCNTn equals the OCRnx value, the compare match will be missed, resulting in incorrect wave-
form generation. Do not write the TCNTn equal to TOP in PWM modes with variable TOP
values. The compare match for the TOP will be ignored and the counter will continue to 0xFFFF.
Similarly, do not write the TCNTn value equal to BOTTOM when the counter is downcounting.
The setup of the OCnx should be performed before setting the Data Direction Register for the
port pin to output. The easiest way of setting the OCnx value is to use the Force Output Com-
pare (FOCnx) strobe bits in Normal mode. The OCnx Register keeps its value even when
changing between Waveform Generation modes.
Be aware that the COMnx1:0 bits are not double buffered together with the compare value.
Changing the COMnx1:0 bits will take effect immediately.
138.
ATmega640/1280/1281/2560/2561
“Accessing 16-bit Registers”
146
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