ATMEGA48V_06 ATMEL [ATMEL Corporation], ATMEGA48V_06 Datasheet - Page 265
ATMEGA48V_06
Manufacturer Part Number
ATMEGA48V_06
Description
8-bit Microcontroller with 8K Bytes In-System Programmable Flash
Manufacturer
ATMEL [ATMEL Corporation]
Datasheet
1.ATMEGA48V_06.pdf
(374 pages)
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24.2.4
24.2.5
2545J–AVR–12/06
Programming Time for Flash when Using SPM
Simple Assembly Code Example for a Boot Loader
A Flash program corruption can be caused by two situations when the voltage is too low. First, a
regular write sequence to the Flash requires a minimum voltage to operate correctly. Secondly,
the CPU itself can execute instructions incorrectly, if the supply voltage for executing instructions
is too low.
Flash corruption can easily be avoided by following these design recommendations (one is
sufficient):
1. Keep the AVR RESET active (low) during periods of insufficient power supply voltage.
2. Keep the AVR core in Power-down sleep mode during periods of low V
The calibrated RC Oscillator is used to time Flash accesses.
gramming time for Flash accesses from the CPU.
Table 24-1.
Note:
Note that the RWWSB bit will always be read as zero in ATmega48. Nevertheless, it is recom-
mended to check this bit as shown in the code example, to ensure compatibility with devices
supporting Read-While-Write.
Flash write (Page Erase, Page Write, and
write Lock bits by SPM)
This can be done by enabling the internal Brown-out Detector (BOD) if the operating volt-
age matches the detection level. If not, an external low V
used. If a reset occurs while a write operation is in progress, the write operation will be
completed provided that the power supply voltage is sufficient.
vent the CPU from attempting to decode and execute instructions, effectively protecting
the SPMCSR Register and thus the Flash from unintentional writes.
.equ PAGESIZEB = PAGESIZE*2
.org SMALLBOOTSTART
Write_page:
;-the routine writes one page of data from RAM to Flash
; the first data location in RAM is pointed to by the Y pointer
; the first data location in Flash is pointed to by the Z-pointer
;-error handling is not included
;-the routine must be placed inside the Boot space
; (at least the Do_spm sub routine). Only code inside NRWW section can
; be read during Self-Programming (Page Erase and Page Write).
;-registers used: r0, r1, temp1 (r16), temp2 (r17), looplo (r24),
; loophi (r25), spmcrval (r20)
; storing and restoring of registers is not included in the routine
; register usage can be optimized at the expense of code size
;-It is assumed that either the interrupt table is moved to the Boot
; loader section or that the interrupts are disabled.
; Page Erase
ldi
rcallDo_spm
; re-enable the RWW section
ldi
1. Minimum and maximum programming time is per individual operation.
spmcrval, (1<<PGERS) | (1<<SELFPRGEN)
spmcrval, (1<<RWWSRE) | (1<<SELFPRGEN)
SPM Programming Time
Symbol
(1)
;PAGESIZEB is page size in BYTES, not words
Min Programming Time
3.7 ms
CC
ATmega48/88/168
Table 25-5
reset protection circuit can be
Max Programming Time
shows the typical pro-
CC
. This will pre-
4.5 ms
265
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