Rainbow Electronics ATtiny43U - Manual (Page 141)

141
8048B–AVR–03/09
Notes: 1. See “Power Management and Sleep Modes” on page 31 for details.
2. The default value of SUT1..0 results in maximum start-up time for the default clock source.
See Table 6-5 on page 26 for details.
3. The default setting of CKSEL3..0 results in internal RC Oscillator @ 8.0 MHz. See Table 6-4
on page 25 for details.
Note that fuse bits are locked if Lock Bit 1 (LB1) is programmed. Fuse bits should be pro-
grammed before lock bits. The status of fuse bits is not affected by chip erase.
Fuse bits can also be read by device firmware. See section “Reading the Fuse and Lock Bits
from Software” on page 135 .
19.2.1 Latching of Fuses
Fuse values are latched when the device enters programming mode and changes to fuse values
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. Fuses are also latched on power-up.
19.3 Device Signature Imprint Table
The device signature imprint table is a dedicated memory area used for storing miscellaneous
device information, such as the device signature and oscillator calibaration data. Most of this
memory segment is reserved for internal use, as outlined in
Table 19-6 .
Notes: 1. See section “Signature Bytes” for more information.
2. See section “Calibration Byte” for more information.
Table 19-5. Fuse Low Byte
Fuse Low Byte Bit No Description Default Value
CKDIV8 (1) 7 Divide clock by 8 0 (programmed)
CKOUT 6 Clock Output Enable 1 (unprogrammed)
SUT1 5 Select start-up time 1 (unprogrammed) (2)
SUT0 4 Select start-up time 0 (programmed) (2)
CKSEL3 3 Select Clock source 0 (programmed) (3)
CKSEL2 2 Select Clock source 0 (programmed) (3)
CKSEL1 1 Select Clock source 1 (unprogrammed) (3)
CKSEL0 0 Select Clock source 0 (programmed) (3)
Table 19-6. Contents of Device Signature Imprint Table.
Address High Byte
0x00 Signature byte 0 (1)
0x01 Calibration data for internal oscillator (2)
0x02 Signature byte 1 (1)
0x03 Reserved for internal use
0x04 Signature byte 2 (1)
0x05 ... 0x2A Reserved for internal use