RFPIC12C509AG Microchip Technology Inc., RFPIC12C509AG Datasheet - Page 54

• Manufacturer Part Number: RFPIC12C509AG
• Description: 18/20-pin 8-bit Cmos Microcontroller With Uhf Ask/fsk Transmitter
• Manufacturer: Microchip Technology Inc.

Watchdog Timer (WDT) Reset.
dips below its minimum value, but not to zero, and then
recovers. The device should be RESET in the event of
a Brown-out.
To RESET the rfPIC12C509AG/509AF when a Brown-out
occurs, external Brown-out protection circuits may be built,
as shown in Figure 8-11, Figure 8-12 and Figure 8-13.
rfPIC12C509AG/509AF
8.7
The TO, PD, and GPWUF bits in the STATUS register
can be tested to determine if a RESET condition has
been caused by a power-up condition, a MCLR or
TABLE 8-7:
8.7.1
A Brown-out is a condition where device power (V
FIGURE 8-11:
DS70031A-page 52
GPWUF TO
Legend: u = unchanged
Note 1: The TO, PD, and GPWUF bits maintain
This circuit will activate RESET when V
below Vz + 0.7V (where Vz = Zener voltage).
*Refer to Figure 8-5 and Table 11-1 for internal
weak pull-up on MCLR.
0
0
0
0
0
1
33k
V
Time-Out Sequence, Power Down,
and Wake-up from SLEEP Status
Bits (TO/PD/GPWUF)
DD
their status (u) until a RESET occurs. A
low-pulse on the MCLR input does not
change the TO, PD, and GPWUF status
bits.
RESET ON BROWN-OUT
0
0
1
1
u
1
10k
PD
TO/PD/GPWUF STATUS
AFTER RESET
0
u
0
1
u
0
BROWN-OUT
PROTECTION CIRCUIT 1
WDT wake-up from
SLEEP
WDT time-out (not from
SLEEP)
MCLR wake-up from
SLEEP
Power-up
MCLR not during SLEEP
Wake-up from SLEEP on
pin change
Q1
40k*
V
DD
RESET caused by
rfPIC12C509AG/
509AF
V
DD
MCLR
DD
goes
Preliminary
DD
)
FIGURE 8-12:
FIGURE 8-13:
This Brown-out circuit is less expensive, although
less accurate. Transistor Q1 turns off when V
is below a certain level such that:
*Refer to Figure 8-5 and Table 11-1 for internal
weak pull-up on MCLR.
This
Microchip Technology’s MCP809 microcontroller
supervisor. The MCP8XX and MCP1XX family of
supervisors provide push-pull and open collector
outputs with both high and low active RESET
pins. There are 7 different trip point selections to
accommodate 5V and 3V systems.
Vss
MCP809
RST
Brown-out
R1
R2
V
DD
V
V
V
DD
DD
DD
capacitor
•
bypass
BROWN-OUT
PROTECTION CIRCUIT 2
BROWN-OUT
PROTECTION CIRCUIT 3
protection
R1 + R2
©
2001 Microchip Technology Inc.
R1
Q1
40k*
V
DD
= 0.7V
rfPIC12C509AG/
509AF
V
rfPIC12C509AG/
509AF
V
circuit
DD
DD
MCLR
MCLR
employs
DD