cop8cce9imt9 National Semiconductor Corporation, cop8cce9imt9 Datasheet - Page 24

• Manufacturer Part Number: cop8cce9imt9
• Description: 8-bit Cmos Flash Microcontroller With 8k Memory, Virtual Eeprom, 10-bit A/d And Brownout Reset
• Manufacturer: National Semiconductor Corporation

www.national.com
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 V
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
The internal reset will not be turned off until the Idle Timer
underflows. The internal reset will perform the same func-
tions 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
above the 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
CC
drops below a voltage of about 1.8V. The device will
CC
is greater than V
transients (glitches). It is essential that good
rises above the trigger voltage (approximately
CC
bor
rises from 0V and the on-chip RESET is
.
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
) is started and the Idle
d
C
has expired, the Idle
. This delay starts as
d
has expired before
FIGURE 10. Brownout Reset Operation
CC
CC
drops below
drops below
CC
(Continued)
CC
remains
rises
CC
is
24
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 two 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 high brownout voltage. Low brownout
voltage devices are guaranteed to operate at 3.33MHz down
to the low brownout voltage. Low brownout voltage de-
vices 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 only the on-chip Brownout Reset feature is being
used, the RESET pin should be connected directly to V
The RESET input may also be connected to an external
pull-up resistor or to other external circuitry. The output of the
brownout reset detector will always preset the Idle Timer to a
value between 00F0 and 00FF (240 to 256 t
the internal reset will be generated.
The contents of data registers and RAM are unknown fol-
lowing the on-chip reset.
COP8CBE, V
COP8CCE, V
CC
be done to ensure that the brownout feature
bor
bor
= low voltage range
= high voltage range
20022513
C
). At this time,
bor
volt-
CC
.