attiny24v ATMEL Corporation, attiny24v Datasheet - Page 157

• Manufacturer Part Number: attiny24v
• Description: 8-bit Avr Microcontroller With 2/4/8k Bytes Insystem Programmable Flash
• Manufacturer: ATMEL Corporation

18.7
18.8
18.9
18.9.1
8006H–AVR–10/09
Preventing Flash Corruption
Programming Time for Flash when Using SPM
Register Description
SPMCSR – Store Program Memory Control and Status Register
If successful, the contents of the destination register are as described in section
ture Imprint Table” on page
During periods of low V
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. 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):
The calibrated RC Oscillator is used to time Flash accesses.
gramming time for Flash accesses from the CPU.
Table 18-1.
Note:
The Store Program Memory Control and Status Register contains the control bits needed to con-
trol the Program memory operations.
• Bits 7..6 – Res: Reserved Bits
These bits are reserved and always read as zero.
Bit
0x37 (0x57)
Read/Write
Initial Value
Flash write (Page Erase, Page Write, and
write Lock bits by SPM)
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
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
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.
vent the CPU from attempting to decode and execute instructions, effectively protecting
the SPMCSR Register and thus the Flash from unintentional writes.
1. The min and max programming times is per individual operation.
SPM Programming Time
Symbol
R
7
–
0
CC
, the Flash program can be corrupted because the supply voltage is
R
6
–
0
161.
RSIG
R
5
0
(1)
Min Programming Time
CTPB
R/W
4
0
3.7 ms
RFLB
R/W
3
0
PGWRT
Table 18-1
R/W
2
0
CC
ATtiny24/44/84
reset protection circuit
Max Programming Time
PGERS
R/W
1
0
shows the typical pro-
CC
. This will pre-
4.5 ms
SPMEN
R/W
“Device Signa-
0
0
SPMCSR
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