DSPIC30F2011 datasheet(127/206 Pages) MICROCHIP

127 / 206 page

DS70139F-page 127

dsPIC30F2011/2012/3012/3013

17.3

Reset

The PIC18F1220/1320 differentiates between various

kinds of Reset:

a) Power-on Reset (POR)

b) MCLR Reset during normal operation

MCLR Reset during Sleep

d) Watchdog Timer (WDT) Reset (during normal

operation)

e) Programmable Brown-out Reset (BOR)

RESET Instruction

g) Reset caused by trap lockup (TRAPR)

h) Reset caused by illegal opcode or by using an

uninitialized W register as an address pointer

(IOPUWR)

Different registers are affected in different ways by

various Reset conditions. Most registers are not

affected by a WDT wake-up since this is viewed as the

resumption of normal operation. Status bits from the

RCON register are set or cleared differently in different

Reset situations, as indicated in Table 17-5. These bits

are used in software to determine the nature of the

Reset.

A block diagram of the On-Chip Reset Circuit is shown

in Figure 17-2.

A MCLR noise filter is provided in the MCLR Reset

path. The filter detects and ignores small pulses.

Internally generated Resets do not drive MCLR pin low.

FIGURE 17-2:

RESET SYSTEM BLOCK DIAGRAM

17.3.1

POR: POWER-ON RESET

A power-on event will generate an internal POR pulse

when a VDD rise is detected. The Reset pulse will occur

at the POR circuit threshold voltage (VPOR) which is

nominally

1.85V.

The

device

supply

voltage

characteristics must meet specified starting voltage

and rise rate requirements. The POR pulse will reset a

POR timer and place the device in the Reset state. The

POR also selects the device clock source identified by

the oscillator configuration fuses.

The POR circuit inserts a small delay, TPOR, which is

nominally 10

μs and ensures that the device bias

circuits are stable. Furthermore, a user selected

power-up time-out (TPWRT) is applied. The TPWRT

parameter is based on device Configuration bits and

can be 0 ms (no delay), 4 ms, 16 ms or 64 ms. The total

delay is at device power-up, TPOR + TPWRT. When

these delays have expired, SYSRST will be negated on

the next leading edge of the Q1 clock and the PC will

jump to the Reset vector.

The timing for the SYSRST signal is shown in

Figure 17-3 through Figure 17-5.

MCLR

VDD

VDD Rise

Detect

POR

SYSRST

Sleep or Idle

Brown-out

Reset

BOREN

RESET

Instruction

WDT

Module

Digital

Glitch Filter

BOR

Trap Conflict

Illegal Opcode/

Uninitialized W Register

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