at89lp216-20xi ATMEL Corporation, at89lp216-20xi Datasheet - Page 14

• Manufacturer Part Number: at89lp216-20xi
• Description: At89lp216 8-bit Microcontroller With 2k Bytes Flash
• Manufacturer: ATMEL Corporation

10.2
10.3
14
Brown-out Reset
External Reset
AT89LP216
Table 10-1.
The AT89LP216 has an on-chip Brown-out Detection (BOD) circuit for monitoring the V
during operation by comparing it to a fixed trigger level. The trigger level for the BOD is nomi-
nally 2.2V. The purpose of the BOD is to ensure that if V
the system will gracefully enter reset without the possibility of errors induced by incorrect execu-
tion. A BOD sequence is shown in
trigger level V
trigger level, the start-up timer releases the internal reset after the specified time-out period has
expired
(See “User Configuration Fuses” on page
Figure 10-3. Brown-out Detector Reset
The P1.3/RST pin can function as either an active-LOW reset input or as a digital general-
purpose I/O, P1.3. The Reset Pin Enable Fuse, when set to “1”, enables the external reset input
function on P1.3.
used as an input or output pin. When configured as a reset input, the pin must be held low for at
least two clock cycles to trigger the internal reset.
Note:
SUT Fuse 1
Time-out
Internal
Reset
V
0
0
1
1
(Table
During a power-up sequence, the fuse selection is always overridden and therefore the pin will
always function as a reset input. An external circuit connected to this pin should not hold this
pin LOW during a power-on sequence as this will keep the device in reset until the pin tran-
sitions high. After the power-up delay, this input will function either as an external reset input or
as a digital input as defined by the fuse bit. Only a power-up reset will temporarily override the
selection defined by the reset fuse bit. Other sources of reset will not override the reset fuse bit.
P1.3/RST also serves as the In-System Programming (ISP) enable. ISP is enabled when the
external reset pin is held low. When the reset pin is disabled by the fuse, ISP may only be entered
by pulling P1.3 low during power-up.
CC
BOD
Start-up Timer Settings
V POR
10-1). The Brown-out Detector must be enabled by setting the BOD Enable Fuse.
, the internal reset is immediately activated. When V
(See “User Configuration Fuses” on page
SUT Fuse 0
0
1
0
1
Clock Source
Internal RC/External Clock
Crystal Oscillator
Internal RC/External Clock
Crystal Oscillator
Internal RC/External Clock
Crystal Oscillator
Internal RC/External Clock
Crystal Oscillator
Figure
71.).
10-3. When V
V BOD
t SUT
CC
fails or dips while executing at speed,
CC
71.). When cleared, P1.3 may be
decreases to a value below the
CC
increases above the
t
SUT
3621B–MICRO–11/07
16384
(± 5%) µs
1024
2048
1024
4096
4096
512
16
CC
level