ATA8742 ATMEL Corporation, ATA8742 Datasheet - Page 182

• Manufacturer Part Number: ATA8742
• Manufacturer: ATMEL Corporation

28.2.1
28.3
28.4
182
Signature Bytes
Calibration Byte
ATA8742
Latching of Fuses
Table 28-5.
Notes:
The status of the Fuse bits is not affected by Chip Erase. Note that the Fuse bits are locked if
Lock bit1 (LB1) is programmed. Program the Fuse bits before programming the Lock bits.
The fuse values are latched when the device enters programming mode and changes of the
fuse values will have no effect until the part leaves Programming mode. This does not apply to
the EESAVE Fuse which will take effect once it is programmed. The fuses are also latched on
Power-up in Normal mode.
All Atmel microcontrollers have a three-byte signature code which identifies the device. This
code can be read in both serial and High-voltage Programming mode, also when the device is
locked. The three bytes reside in a separate address space. For the ATtiny24/44/84 the signa-
ture bytes are given in
Table 28-6.
Signature area of the ATtiny24/44/84 has one byte of calibration data for the internal RC Oscilla-
tor. This byte resides in the high byte of address 0x000. During reset, this byte is automatically
written into the OSCCAL Register to ensure correct frequency of the calibrated RC Oscillator.
Fuse Low Byte
CKDIV8
CKOUT
SUT1
SUT0
CKSEL3
CKSEL2
CKSEL1
CKSEL0
Parts
ATtiny24
ATtiny44
ATtiny84
1. See
2. The default value of SUT1..0 results in maximum start-up time for the default clock source.
3. The default setting of CKSEL3..0 results in internal RC Oscillator @ 8.0 MHz. See
(1)
See
on page 45
Fuse Low Byte
Device ID
“System Clock Prescaler” on page 47
Table 14-7 on page 45
for details.
Table
Bit No
28-6.
7
6
5
4
3
2
1
0
0x000
0x1E
0x1E
0x1E
for details.
Description
Divide clock by 8
Clock Output Enable
Select start-up time
Select start-up time
Select Clock source
Select Clock source
Select Clock source
Select Clock source
Signature Bytes Address
for details.
0x001
0x91
0x93
0x92
Default Value
0 (programmed)
1 (unprogrammed)
1 (unprogrammed)
0 (programmed)
0 (programmed)
0 (programmed)
1 (unprogrammed)
0 (programmed)
9151A–INDCO–07/09
0x002
0x0C
(2)
(3)
(3)
(3)
0x0B
0x07
(2)
(3)
Table 14-6