MPC5200B datasheet(14/72 Pages) FREESCALE

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MPC5200B Data Sheet, Rev. 3

Freescale Semiconductor

1.3.4

Resets

The MPC5200B has three reset pins:

•

PORRESET - Power on Reset

•HRESET - Hard Reset

•SRESET - Software Reset

These signals are asynchronous I/O signals and can be asserted at any time. The input side uses a Schmitt trigger and requires

the same input characteristics as other MPC5200B inputs, as specified in the DC Electrical Specifications section. Table 14

specifies the pulse widths of the Reset inputs.

For PORRESET the value of the minimum pulse width reflects the power on sequence. If PORRESET is asserted afterwards

its minimum pulse width equals the minimum given for HRESET related to the same reference clock.

The tVDD_stable describes the time which is needed to get all power supplies stable.

For tlock, refer to the Oscillator/PLL section of this specification for further details.

For tup_osc, refer to the Oscillator/PLL section of this specification for further details.

Following the deassertion of PORRESET, HRESET and SRESET remain low for 4096 reference clock cycles.

The deassertion of HRESET for at least the minimum pulse width forces the internal resets to be active for an additional 4096

clock cycles.

NOTE

As long as VDD is not stable the HRESET output is not stable.

NOTE

Make sure that the PORRESET does not carry any glitches. The MPC5200B has no filter

to prevent them from getting into the chip. HRESET and SRESET must have a monotonous

rise time. The assertion of HRESET becomes active at Power on Reset without any

SYS_XTAL clock.

Table 14. Reset Pulse Width

Name

Description

Min Pulse Width

Max Pulse

Width

Reference Clock

SpecID

PORRESET

Power On Reset

tVDD_stable+tup_osc+tlock

—

SYS_XTAL_IN

A3.1

HRESET

Hardware Reset

4 clock cycles

—

SYS_XTAL_IN

A3.2

SRESET

Software Reset

4 clock cycles

—

SYS_XTAL_IN

A3.3

Table 15. Reset Rise/Fall Timing

Description

Min

Max

Unit

SpecID

PORRESET fall time

—

A3.4

PORRESET rise time

—

A3.5

HRESET fall time

—

A3.6

HRESET rise time

—

A3.7

SRESET fall time

—

A3.8

SRESET rise time

—

A3.9

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