32
XMEGA B [DATASHEET]
8291B–AVR–01/2013
4.15.4 FUSEBYTE4 – Fuse Byte 4
Bit 7:5 – Reserved
These fuse bits are reserved. For compatibility with future devices, always write these bits to one when this register is
written.
Bit: 4 – RSTDISBL: External Reset Disable
This fuse can be programmed to disable the external reset pin functionality. When this is done, pulling the reset pin low
will not cause an external reset. A reset is required before this bit will be read correctly after it is changed.
Bit 3:2 – STARTUPTIME[1:0]: Start-up time
These fuse bits can be used to set at a programmable timeout period from when all reset sources are released until the
internal reset is released from the delay counter. A reset is required before these bits will be read correctly after they are
changed.
The delay is timed from the 1kHz output of the ULP oscillator. Refer to
Table 4-4.
Start-up time.
Bit 1 – WDLOCK: Watchdog Timer Lock
The WDLOCK fuse can be programmed to lock the watchdog timer configuration. When this fuse is programmed, the
watchdog timer configuration cannot be changed, and the ENABLE bit in the watchdog CTRL register is automatically set
at reset and cannot be cleared from the application software. The WEN bit in the watchdog WINCTRL register is not set
automatically, and needs to be set from software. A reset is required before this bit will be read correctly after it is
changed.
Table 4-5.
Watchdog timer lock.
Bit 0 – JTAGEN: JTAG Enabled
This fuse controls whether or not the JTAG interface is enabled.
When the JTAG interface is disabled, all access through JTAG is prohibited, and the device can be accessed using only
the program and debug interface (PDI). The JTAGEN fuse is available only on devices with JTAG interface. A reset is
required before this bit will be read correctly after it is changed.
Bit
7
6
5
4
3
2
1
0
+0x04
–
–
–
RSTDISBL
STARTUPTIME[1:0]
WDLOCK
JTAGEN
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
1
1
1
1
1
1
1
0
STARTUPTIME[1:0]
1kHz ULP oscillator cycles
00
64
01
4
10
Reserved
11
0
WDLOCK
Description
0
Watchdog timer locked for modifications
1
Watchdog timer not locked
Содержание XMEGA B
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