PIC18C242 MICROCHIP [Microchip Technology], PIC18C242 Datasheet - Page 25

• Manufacturer Part Number: PIC18C242
• Description: High-Performance Microcontrollers with 10-Bit A/D
• Manufacturer: MICROCHIP [Microchip Technology]

3.6
On power-up, the time-out sequence is as follows: First,
PWRT time-out is invoked after the POR time delay has
expired. Then, OST is activated. The total time-out will
vary based on oscillator configuration and the status of
the PWRT. For example, in RC mode with the PWRT
disabled, there will be no time-out at all. Figure 3-3,
Figure 3-4, Figure 3-5, Figure 3-6 and Figure 3-7
depict time-out sequences on power-up.
TABLE 3-1:
Register 3-1:
TABLE 3-2:
Oscillator
Configuration
HS with PLL enabled
HS, XT, LP
EC
External RC
Note 1: 2 ms = Nominal time required for the 4x PLL to lock.
bit 7
Condition
Power-on Reset
MCLR Reset during normal
operation
Software Reset during normal
operation
Stack Full Reset during normal
operation
Stack Underflow Reset during
normal operation
MCLR Reset during SLEEP
WDT Reset
WDT Wake-up
Brown-out Reset
Interrupt wake-up from SLEEP
Legend: u = unchanged, x = unknown, — = unimplemented bit read as '0'.
Note 1: When the wake-up is due to an interrupt and the GIEH or GIEL bits are set, the PC is loaded with the
7/99 Microchip Technology Inc.
R/W-0
IPEN
2: 72 ms is the nominal power-up timer delay
Time-out Sequence
interrupt vector (0x000008h or 0x000018h).
R/W-0
LWRT
TIME-OUT IN VARIOUS SITUATIONS
RCON Register Bits and Positions
STATUS BITS, THEIR SIGNIFICANCE AND THE INITIALIZATION CONDITION FOR
RCON REGISTER
(1)
Power-up
PWRTE = 0
72 ms + 1024Tosc + 2ms 1024Tosc + 2 ms 72 ms + 1024Tosc + 2ms 1024Tosc + 2 ms
72 ms + 1024Tosc
72 ms
72 ms
U-0
—
Program
Counter
0000h
0000h
0000h
0000h
0000h
0000h
0000h
PC + 2
0000h
PC + 2
(2)
R/W-1
RI
(1)
RCON
Register
00-1 1100
00-u uuuu
0u-0 uuuu
0u-u uu11
0u-u uu11
00-u 10uu
0u-u 01uu
uu-u 00uu
0u-1 11u0
uu-u 00uu
Preliminary
PWRTE = 1
1024Tosc
—
—
R/W-1
TO
Since the time-outs occur from the POR pulse, if MCLR
is kept low long enough, the time-outs will expire.
Bringing MCLR high will begin execution immediately
(Figure 3-5). This is useful for testing purposes or to
synchronize more than one PIC18CXXX device operat-
ing in parallel.
Table 3-2 shows the reset conditions for some Special
Function Registers, while Table 3-3 shows the reset
conditions for all the registers.
R/W-1
RI
1
u
0
u
u
u
1
u
1
u
PD
Brown-out
72 ms + 1024Tosc
72 ms
72 ms
TO
u
u
u
u
1
0
0
1
1
1
R/W-1
PD
POR
1
u
u
u
u
0
1
0
1
0
POR
(2)
0
u
u
u
u
u
u
u
1
u
bit 0
R/W-1
BOR
PIC18CXX2
BOR
0
u
u
u
u
u
u
u
0
u
Wake-up from
SLEEP or
Oscillator Switch
1024Tosc
—
—
STKFUL
DS39026B-page 25
u
u
u
u
1
u
u
u
u
u
STKUNF
u
u
u
1
u
u
u
u
u
u