ATmega406 Atmel Corporation, ATmega406 Datasheet - Page 179
ATmega406
Manufacturer Part Number
ATmega406
Description
Manufacturer
Atmel Corporation
Specifications of ATmega406
Flash (kbytes)
40 Kbytes
Pin Count
48
Max. Operating Frequency
1 MHz
Cpu
8-bit AVR
# Of Touch Channels
8
Hardware Qtouch Acquisition
No
Max I/o Pins
18
Ext Interrupts
4
Usb Speed
No
Usb Interface
No
Twi (i2c)
1
Graphic Lcd
No
Video Decoder
No
Camera Interface
No
Adc Channels
11
Adc Resolution (bits)
12
Adc Speed (ksps)
1.9
Resistive Touch Screen
No
Temp. Sensor
Yes
Crypto Engine
No
Sram (kbytes)
2
Eeprom (bytes)
512
Self Program Memory
YES
Dram Memory
No
Nand Interface
No
Picopower
No
Temp. Range (deg C)
-30 to 85
I/o Supply Class
4.0 to 25
Operating Voltage (vcc)
4.0 to 25
Fpu
No
Mpu / Mmu
no / no
Timers
2
Output Compare Channels
3
Pwm Channels
2
32khz Rtc
Yes
Calibrated Rc Oscillator
Yes
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Part Number:
ATmega406-1AAU
Manufacturer:
AT
Quantity:
20 000
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27.3
27.3.1
27.3.2
2548E–AVR–07/06
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
8 on page 193
• 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 a
call/jmp/lpm 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 sec-
tion. 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 com-
pleted, the RWWSB must be cleared by software before reading code located in the RWW
section.
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 27-1.
Address During the Programming?
read during the operation.
entire operation.
Which Section does the Z-pointer
See Section “27.5.1” on page 183.
NRWW Section
RWW Section
Read-While-Write Features
and
Figure 27-2 on page
Which Section Can be Read
During Programming?
181. The main difference between the two sections is:
for details on how to clear RWWSB.
NRWW Section
None
Halted?
CPU
Yes
No
ATmega406
Read-While-Write
Supported?
Yes
No
Table 27-
179
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