AT90CAN128-16AE ATMEL Corporation, AT90CAN128-16AE Datasheet - Page 319

• Manufacturer Part Number: AT90CAN128-16AE
• Description: 8-bit Avr Microcontroller With 128K Bytes of Isp Flash And CAN Controller.flash (Kbytes) 128 Vcc (V) 2.7-5.5 EEPROM (Kbytes) 4 SRAM (bytes) 4K CAN (mess. Obj.) 15
• Manufacturer: ATMEL Corporation

Preventing Flash Corruption
Programming Time for Flash
when Using SPM
Simple Assembly Code
Example for a Boot Loader
4250C–CAN–03/04
When reading the Extended Fuse byte, load 0x0002 in the Z-pointer. When an LPM
instruction is executed within three cycles after the BLBSET and SPMEN bits are set in
the SPMCSR, the value of the Extended Fuse byte (EFB) will be loaded in the destina-
tion register as shown below. Refer to Table 123 on page 324 for detailed description
and mapping of the Extended Fuse byte.
Fuse and Lock bits that are programmed, will be read as zero. Fuse and Lock bits that
are unprogrammed, will be read as one.
During periods of low V
age is too low for the CPU and the Flash to operate properly. These issues are the same
as for board level systems using the Flash, and the same design solutions should be
applied.
A Flash program corruption can be caused by two situations when the voltage is too low.
•
•
Flash corruption can easily be avoided by following these design recommendations (one
is sufficient):
1. If there is no need for a Boot Loader update in the system, program the Boot
2. Keep the AVR RESET active (low) during periods of insufficient power supply
3. Keep the AVR core in Power-down sleep mode during periods of low V
The calibrated RC Oscillator is used to time Flash accesses. Table 117 shows the typi-
cal programming time for Flash accesses from the CPU.
Table 117. SPM Programming Time
Bit
Rd (Z=0x0002)
Flash write (Page Erase, Page Write,
and write Lock bits by SPM)
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.
Loader Lock bits to prevent any Boot Loader software updates.
voltage. This can be done by enabling the internal Brown-out Detector (BOD) if
the operating voltage matches the detection level. If not, an external low V
reset protection circuit can be 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.
will prevent the CPU from attempting to decode and execute instructions, effec-
tively protecting the SPMCSR Register and thus the Flash from unintentional
writes.
;- 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),
Symbol
7
–
CC
6
–
, the Flash program can be corrupted because the supply volt-
5
–
Min Programming Time
4
–
3.7 ms
EFB3
3
EFB2
2
AT90CAN128
Max Programming Time
EFB1
1
4.5 ms
EFB0
0
CC
. This
CC
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