Datasheet

180
8246A–AVR–11/09
ATtiny2313A/4313
Notes: 1. The default value of SUT1..0 results in maximum start-up time for the default clock source.
See Table 6-4 on page 27 for details.
2. The default setting of CKSEL3..0 results in internal RC Oscillator @ 8 MHz.
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.
Fuse bits can also be read by device firmware. See section “Reading the Fuse and Lock Bits” on
page 189.
20.2.1 Latching of Fuses
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.
20.3 Device Signature Imprint Table
The device signature imprint table is a dedicated read only memory area used for storing miscel-
laneous device information, such as the device signature and oscillator calibration data. Most of
this memory segment is reserved for internal use, as outlined in Table 20-6.
Byte addresses are used when the device itself reads the data with the LPM command. External
programming devices must use word addresses.
Table 20-5. Fuse Low Byte
Fuse Low Byte Bit No Description Default Value
CKDIV8 7 Divide clock by 8 0 (programmed)
CKOUT 6 Output Clock on CKOUT pin 1 (unprogrammed)
SUT1 5 Select start-up time 1 (unprogrammed)
(1)
SUT0 4 Select start-up time 0 (programmed)
(1)
CKSEL3 3 Select Clock source 0 (programmed)
(2)
CKSEL2 2 Select Clock source 1 (unprogrammed)
(2)
CKSEL1 1 Select Clock source 0 (programmed)
(2)
CKSEL0 0 Select Clock source 0 (programmed)
(2)
Table 20-6. Contents of Device Signature Imprint Table.
Word Address Byte Address High Byte
0x00
0x00 Signature byte 0
(1)
0x01 Calibration data for internal 8 MHz oscillator
(2)
0x01
0x02 Signature byte 1
(1)
0x03 Calibration data for internal 4 MHz oscillator
(2)
0x02
0x04 Signature byte 2
(1)
0x05 ... Reserved for internal use