Datasheet

251
7734Q–AVR–02/12
AT90PWM81/161
Note: 1. The default value of SUT1..0 results in maximum start-up time for the default clock source.
See Table 5-4 on page 30 for details.
2. The default setting of CKSEL3..0 results in internal RC Oscillator @ 8MHz. See Table 5-1 on
page 28 for details.
3. The CKOUT Fuse allows the system clock to be output on PORTD0. See “Clock Output Buf-
fer” on page 34 for details.
4. See “System Clock Prescaler” on page 39 for details.
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.
21.2.3 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.
21.3 Signature Bytes
All Atmel microcontrollers have a three-byte signature code which identifies the device. This
code can be read in both serial and parallel mode, also when the device is locked. The three
bytes reside in a separate address space, the signature row.
21.3.1 Signature Bytes
Table 21-7. Device ID bytes for AT90PWM81/161 devices.
For the AT90PWM81/161 the signature bytes are:
1. 0x000: 0x1E (indicates manufactured by Atmel).
2. 0x002: 0x93 (indicates 8KB Flash memory).
3. 0x004: 0x88 (indicates the AT90PWM81 device when 0x002 is 0x93).
0x004: 0x8B (indicates the AT90PWM161 device when 0x002 is 0x94).
Table 21-6. Fuse Low byte.
Low Fuse byte Bit no. Description Default value
CKDIV8
(4)
7 Divide clock by 8 0 (programmed)
CKOUT
(3)
6 Clock output 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 0 (programmed)
(2)
CKSEL1 1 Select clock source 1 (unprogrammed)
(2)
CKSEL0 0 Select clock source 0 (programmed)
(2)
Device Device ID bytes
0x004 0x002 0x000
AT9 0PWM 81 88 9 3 1E
AT90PWM161 8B 94 1E