cop8ccr9 National Semiconductor Corporation, cop8ccr9 Datasheet - Page 25

• Manufacturer Part Number: cop8ccr9
• Description: 8-bit Cmos Flash Microcontroller With 32k Memory, Virtual Eeprom, 10-bit A/d And Brownout
• Manufacturer: National Semiconductor Corporation

10.0 Functional Description
One exception to the above is that the brownout circuit will
insert a delay of approximately 3 ms on power up or any time
the V
be held in Reset for the duration of this delay before the Idle
Timer starts counting the 240 to 256 t
soon as the V
mately 1.8V). This behavior is shown in Figure 10.
In Case 1, V
undefined until the supply is greater than approximately
1.0V. At this time the brownout circuit becomes active and
holds the device in RESET. As the supply passes a level of
about 1.8V, a delay of about 3 ms (t
Timer is preset to a value between 00F0 and 00FF (hex).
Once V
Timer is allowed to count down (t
Case 2 shows a subsequent dip in the supply voltage which
goes below the approximate 1.8V level. As V
V
back above the 1.8V level, t
supply rise time is longer for this case, t
V
greater than V
Case 3 shows a dip in the supply where V
V
V
goes back above V
If the Brownout Reset feature is enabled, the internal reset
will not be turned off until the Idle Timer underflows. The
internal reset will perform the same functions as external
reset. The device is guaranteed to operate at the specified
frequency down to the specified brownout voltage. After the
underflow, the logic is designed such that no additional
internal resets occur as long as V
brownout voltage.
The device is relatively immune to short duration negative-
going V
bor
CC
bor
CC
, the internal RESET signal is asserted. When V
, but not below 1.8V. On-chip RESET is asserted when
rises above V
goes below V
CC
CC
drops below a voltage of about 1.8V. The device will
CC
is greater than V
transients (glitches). It is essential that good
CC
bor
CC
.
rises from 0V and the on-chip RESET is
rises above the trigger voltage (approxi-
bor
bor
bor
and t
.
and t
id
id
bor
starts immediately when V
d
starts as soon as the supply
is started. Since the power
and t
id
).
d
CC
) is started and the Idle
d
C
has expired, the Idle
. This delay starts as
d
remains above the
has expired before
FIGURE 10. Brownout Reset Operation
CC
CC
drops below
drops below
(Continued)
CC
rises
CC
is
25
filtering of V
works correctly. Power supply decoupling is vital even in
battery powered systems.
There are two optional brownout voltages. The part numbers
for the three versions of this device are:
Refer to the device specifications for the actual V
ages.
High brownout voltage devices are guaranteed to operate at
10MHz down to the brownout voltage. Low brownout voltage
devices are guaranteed to operate at 3.33MHz down to the
brownout voltage. Devices are not guaranteed to operate
at 10MHz down to the low brownout voltage.
Under no circumstances should the RESET pin be allowed
to float. If the on-chip Brownout Reset feature is being used,
the RESET pin should be connected directly to V
RESET input may also be connected to an external pull-up
resistor or to other external circuitry. Any rising edge on the
RESET pin while V
may cause unpredictable results. The output of the brownout
reset detector will always preset the Idle Timer to a value
between 00F0 and 00FF (240 to 256 t
internal reset will be generated.
If the BOR feature is disabled, then no internal resets are
generated and the Idle Timer will power-up with an unknown
value. In this case, the external RESET must be used. When
BOR is disabled, this on-chip circuitry is disabled and draws
no DC current.
The contents of data registers and RAM are unknown fol-
lowing the on-chip reset.
COP8CBR, V
COP8CCR, V
COP8CDR, BOR is disabled.
CC
be done to ensure that the brownout feature
bor
bor
CC
= low voltage range
= high voltage range
is below the specified operating range
C
). At this time, the
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CC
bor
. The
volt-