ATMEGA644PV ATMEL [ATMEL Corporation], ATMEGA644PV Datasheet - Page 275
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: 275 of 408
- Download datasheet (4Mb)
24.4
24.4.1
24.4.2
8011D–AVR–02/07
Read-While-Write and No Read-While-Write Flash Sections
RWW – Read-While-Write Section
NRWW – No Read-While-Write Section
Whether the CPU supports Read-While-Write or if the CPU is halted during a Boot Loader soft-
ware update is dependent on which address that is being programmed. In addition to the two
sections that are configurable by the BOOTSZ Fuses as described above, the Flash is also
divided into two fixed sections, the Read-While-Write (RWW) section and the No Read-While-
Write (NRWW) section. The limit between the RWW- and NRWW sections is given in
1
• When erasing or writing a page located inside the RWW section, the NRWW section can be
• When erasing or writing a page located inside the NRWW section, the CPU is halted during the
Note that the user software can never read any code that is located inside the RWW section dur-
ing a Boot Loader software operation. The syntax “Read-While-Write section” refers to which
section that is being programmed (erased or written), not which section that actually is being
read during a Boot Loader software update.
If a Boot Loader software update is programming a page inside the RWW section, it is possible
to read code from the Flash, but only code that is located in the NRWW section. During an on-
going programming, the software must ensure that the RWW section never is being read. If the
user software is trying to read code that is located inside the RWW section (i.e., by load program
memory, call, or jump instructions or an interrupt) during programming, the software might end
up in an unknown state. To avoid this, the interrupts should either be disabled or moved to the
Boot Loader section. The Boot Loader section is always located in the NRWW section. The
RWW Section Busy bit (RWWSB) in the Store Program Memory Control and Status Register
(SPMCSR) will be read as logical one as long as the RWW section is blocked for reading. After
a programming is completed, the RWWSB must be cleared by software before reading code
located in the RWW section.
RWWSB.
The code located in the NRWW section can be read when the Boot Loader software is updating
a page in the RWW section. When the Boot Loader code updates the NRWW section, the CPU
is halted during the entire Page Erase or Page Write operation.
Table 24-1.
Address During the Programming?
read during the operation.
entire operation.
and
Which Section does the Z-pointer
Figure 24-1 on page
NRWW Section
RWW Section
Read-While-Write Features
276. The main difference between the two sections is:
See Section “24.9.1” on page 289.
Which Section Can
be Read During
Programming?
NRWW Section
None
ATmega164P/324P/644P
Is the CPU
Halted?
Yes
No
for details on how to clear
Read-While-Write
Supported?
Yes
No
Table 24-
275
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: