HC05V7GRSSLASHD datasheet(57/170 Pages) NXP

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SECTION 6: RESETS

Page 43

MC68HC05V7 Specification Rev. 1.0

Table 6-1:

COP Watchdog Timer Recommendations

6.2.3.5

COP REGISTER

The COP register is shared with the MSB of an unimplemented User Interrupt Vector as

shown in Figure 6-3. Reading this location will return whatever user data has been

programmed at this location. Writing a “0” to the COPR bit in this location will clear the COP

watchdog timer.

Figure 6-3:

COP Watchdog Timer Location

6.2.4

LOW-VOLTAGE RESET (LVR)

The internal low voltage (LVR) reset is generated when VDD falls below the LVR threshold

VLVRI and will be released following a POR delay starting when VDD rises above VLVRR.

The LVR threshold is tested to be above the minimum operating voltage of the

microcontroller and is intended to ensure that the CPU will be held in reset when the VBATT

supply voltage is below reasonable operating limits. However, it should be noted that the

LVR monitors VDD not VBATT. A mask option is provided to disable the LVR when the

device is expected to normally operate at low voltages. Note that the V

DD rise and fall slew

rates (S

VDDR and SVDDF) must be within the specification for proper LVR operation. If the

specification is not met, the circuit will operate properly following a delay of V

DD/Slew rate.

The LVR will generate the RST signal that will reset the CPU and other peripherals. As it is

not possible to determine the level of the internal VDD at the point VBATT recovers (and POR

is not intended to detect a loss of VDD), an LVR will always recover using a POR delay. The

low voltage reset will activate the internal pulldown device connected to the RESET pin.

WAIT Time Less than

COP Time-Out

STOP Instruction

WAIT Time

THEN the

COP Watchdog Timer

should be as follows:

Disable COP

by mask option

converted to reset

Enable or disable COP

by mask option

WAIT Time More than

COP Time-Out

any length

WAIT Time

Acts as STOP

Disable COP

by mask option

converted to reset

IF the following conditions exist:

UNIMPLEMENTED VECTOR &

COP WATCHDOG TIMER

$3FF0

COPR

UNIMPLEMENTED

READ

WRITE

ADDR

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

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