Rainbow-electronics ATmega8HVD Manuel d'utilisateur télécharger pdf (Page 130)

130

8052B–AVR–09/08

ATmega4HVD/8HVD

Note: 1. The default OSCSEL1:0 setting should not be changed. OSCSEL1:0 = ‘00’ is reserved for

test purposes. Other values are reserved for future use.

24.2.2 Low Byte

Notes: 1. See Table 8-1 on page 23 for details about start-up time.

2. The SPIEN Fuse is not accessible in SPI programming mode.

3. See ”WDTCSR – Watchdog Timer Control Register” on page 48 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.

24.2.3 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.

24.3 Signature Bytes

All Atmel microcontrollers have a three-byte signature code which identifies the device. This

code can be read in both Programming mode, also when the device is locked. The three bytes

reside in a separate address space. The signature bytes of ATmega4HVD/8HVD is given in

Table 24-5.

Table 24-4. Fuse Low Byte

Bit No Fuse Low Byte Description Default Value

7WDTON

(3)

Watchdog Timer always on 1 (unprogrammed)

6 EESAVE

EEPROM memory is preserved

through the Chip Erase

1 (unprogrammed, EEPROM

not preserved)

5 SPIEN

(2)

Enable SPI Programming Interface

0 (programmed, SPI prog.

enabled)

4 DWEN Enable debugWIRE 1 (unprogrammed)

3 SELFPRGEN Self Programming enable 1 (unprogrammed)

2SUT2

(1)

Select start-up time 1 (unprogrammed)

1SUT1

(1)

Select start-up time 1 (unprogrammed)

0SUT0

(1)

Select start-up time 1 (unprogrammed)

Table 24-5. Device ID

Part

Signature Bytes Address

0x000 0x001 0x002

ATmega4HVD 0x1E TBD TBD

ATmega8HVD 0x1E 0x93 0x12

1 2 ... 125 126 127 128 129 130 131 132 133 134 135 ... 167 168

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