Z8F021ASH020SC datasheet(39/276 Pages) ZILOG

39 / 276 page

PS022815-0206

Reset, STOP Mode Recovery and Low Voltage Detection

Z8 Encore! XP® 4K Series

Product Specification

Reset, STOP Mode Recovery and Low

Voltage Detection

Overview

The Reset Controller within the Z8 Encore! XP® 4K Series controls Reset and STOP

Mode Recovery operation and provides indication of low supply voltage conditions. In

typical operation, the following events cause a Reset:

• Power-on reset (POR)

• Voltage brown-out (VBO)

• Watch-Dog Timer time-out (when configured by the WDT_RES Flash Option Bit to

initiate a reset)

• External RESET pin assertion (when the alternate RESET function is enabled by the

GPIO register)

• On-chip debugger initiated Reset (OCDCTL[0] set to 1)

When the device is in STOP mode, a STOP Mode Recovery is initiated by either of the

following:

• Watch-Dog Timer time-out

• GPIO Port input pin transition on an enabled STOP Mode Recovery source

The low voltage detection circuitry on the device (available on the 8-pin product versions

only) performs the following functions:

• Generates the VBO reset when the supply voltage drops below a minimum safe level

• Generates an interrupt when the supply voltage drops below a user-defined level (8-pin de-

vice only)

Reset Types

The Z8 Encore! XP® 4K Series provides several different types of Reset operation. STOP

Mode Recovery is considered a form of Reset. Table 9 lists the types of Reset and their

operating characteristics. The System Reset is longer if the external crystal oscillator is

enabled by the Flash option bits, allowing additional time for oscillator start-up.

Z8F021ASH020SC Datasheet(PDF) 39 Page - Zilog, Inc.