Rainbow Electronics AT89LP216 - Manual (Page 13)

13
3621A–MICRO–6/06
AT89LP216 [Preliminary]
Figure 10-1. Power-on Reset Sequence (BOD Disabled)
If the Brown-out Detector (BOD) is also enabled, the start-up timer does not begin counting until
after V
CC
reaches the BOD threshold voltage V
BOD
as shown in Figure 10-2 . However, if this
event occurs prior to the end of the initialization sequence, the timer must first wait for that
sequence to complete before counting.
Figure 10-2. Power-on Reset Sequence (BOD Enabled)
Note: t
POR
is approximately 92 µs ± 5%.
The start-up timer delay is user-configurable with the Start-up Time User Fuses and depends on
the clock source (
Table 10-1 ). The start-up delay should be selected to provide enough settling
time for V
CC
and the selected clock source. The Start-Up Time fuses also control the length of
the start-up time after a Brown-out Reset or when waking up from Power-down during internally
timed mode.
V
CC
RST
Time-out
t
POR + t SUT
t
RHD
V
POR
Internal
Reset
RST
Internal
Reset
V
RH
(RST Tied to V
CC
)
(RST Controlled Externally)
V
POR
V
CC
RST
Time-out t
POR
t
RHD
V
POR
Internal
Reset
RST
Internal
Reset
V
RH
t
SUT
V
BOD
(RST Tied to V
CC
)
(RST Controlled Externally)