Reset

12.3 RESET

The PIC16F87X differentiates between various kinds of RESET:

• Power-on Reset (POR)

• MCLR Reset during normal operation

• MCLR Reset during SLEEP

• WDT Reset (during normal operation)

• WDT Wake-up (during SLEEP)

• Brown-out Reset (BOR)

Some registers are not affected in any RESET condition.

Their status is unknown on POR and unchanged in any other RESET. Most other registers are reset to a “RESET state” on Power-on Reset (POR), on the

MCLR and WDT Reset, on MCLR Reset during SLEEP, and Brown-out Reset (BOR). They are not affected by a WDT Wake-up, which is viewed as the

resumption of normal operation. The TO and PD bits are set or cleared differently in different RESET situations as indicated in Table 12-4. These bits are used in software to determine the nature of the RESET. See Table 12-6 for a full description of RESET states of all registers.

A simplified block diagram of the On-Chip Reset Circuit is shown in Figure 12-4.

These devices have a MCLR noise filter in the MCLR Reset path. The filter will detect and ignore small pulses.

It should be noted that a WDT Reset does not drive MCLR pin low.