PIC16F628-20P Datasheet, PDF (99/170 Pages) Microchip Technology – FLASH-Based 8-Bit CMOS Microcontroller

PIC16F62X
14.5.5 TIMEOUT SEQUENCE
On power-up the timeout sequence is as follows: First
PWRT timeout is invoked after POR has expired. Then
OST is activated. The total timeout will vary based on
oscillator configuration and PWRTE bit status. For
example, in ER mode with PWRTE bit erased (PWRT
disabled), there will be no timeout at all. Figure 14-8,
Figure 14-9 and Figure 14-10 depict timeout
sequences.
Since the timeouts occur from the POR pulse, if MCLR
is kept low long enough, the timeouts will expire. Then
bringing MCLR high will begin execution immediately
(see Figure 14-9). This is useful for testing purposes or
to synchronize more than one PIC16F62X device
operating in parallel.
Table 14-7 shows the RESET conditions for some
special registers, while Table 14-8 shows the RESET
conditions for all the registers.
14.5.6 POWER CONTROL (PCON) STATUS
REGISTER
The Power Control/STATUS register, PCON (address
8Eh) has two bits.
Bit0 is BOD (Brown-out). BOD is unknown on Power-
on Reset. It must then be set by the user and checked
on subsequent RESETS to see if BOD = 0 indicating
that a brown-out has occurred. The BOD STATUS bit is
a don’t care and is not necessarily predictable if the
brown-out circuit is disabled (by setting BODEN bit = 0
in the Configuration word).
Bit1 is POR (Power-on Reset). It is a ‘0’ on Power-on
Reset and unaffected otherwise. The user must write a
‘1’ to this bit following a Power-on Reset. On a
subsequent RESET if POR is ‘0’, it will indicate that a
Power-on Reset must have occurred (VDD may have
gone too low).
TABLE 14-4: TIMEOUT IN VARIOUS SITUATIONS
Oscillator Configuration
Power-up
PWRTE = 0
PWRTE = 1
XT, HS, LP
ER, INTRC, EC
72 ms + 1024 TOSC
72 ms
1024 TOSC
—
Brown-out Detect
Reset
72 ms + 1024 TOSC
72 ms
Wake-up
from SLEEP
1024 TOSC
—
TABLE 14-5: STATUS/PCON BITS AND THEIR SIGNIFICANCE
POR
BOD
TO
PD
0
X
1
1
Power-on Reset
0
X
0
X
Illegal, TO is set on POR
0
X
X
0
Illegal, PD is set on POR
1
0
X
X
Brown-out Detect Reset
1
1
0
u
WDT Reset
1
1
0
0
WDT Wake-up
1
1
u
u
MCLR Reset during normal operation
1
1
1
0
Legend: u = unchanged, x = unknown.
MCLR Reset during SLEEP
TABLE 14-6: SUMMARY OF REGISTERS ASSOCIATED WITH BROWN-OUT
Address Name Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Value on
POR Reset
Value on all
other
RESETS⁽¹⁾
03h
STATUS IRP
RP1
RPO
TO
PD
Z
DC
C
0001 1xxx 000q quuu
8Eh
PCON
—
—
—
—
OSCF Reset POR
BOD ---- 1-0x ---- u-uq
Note 1: Other (non Power-up) Resets include MCLR Reset, Brown-out Detect Reset and Watchdog Timer Reset during normal opera-
tion.
 2003 Microchip Technology Inc.
Preliminary
DS40300C-page 97