Reset State; Signal Functionality Configuration Out Of Reset; Signal State During Reset - Motorola MPC533 Reference Manual

Reset State

• Assert PORESET/TRST to reset the JTAG TAP controller
• Hold JCOMP/RSTI high prior to PORESET/TRST negation and keep high as long
as JTAG mode is required
• (The READI module will be held inactive since only one of the multiplexed
functions JCOMP and RSTI can be asserted at the negation of PORESET/TRST).
JTAG mode is exited by:
• Drive JCOMP/RSTI low.
PORESET/TRST is not in the JTAG scan path.
2.6 Reset State
During reset, a 130-µA (maximum) resistor "weakly pulls" all input signals, with the
exception of the power-supply and clock-related signals, to a value based on conditions
described in Appendix E, "Electrical Characteristics." In reset state, all I/O signals become
inputs, and all outputs (except for CLKOUT, HRESET, and SRESET) are pulled only by
the pull-up/pull-down.
2.6.1

Signal Functionality Configuration Out of Reset

The reset configuration word defines the post-reset functionality of some multiplexed
signals. For details on these signals and how they are configured, refer to Section 7.5.2,
"Hard Reset Configuration Word."
The 2.6-V bus related signals have selectable output buffer drive strengths that are
controlled by the COM0 bit in the USIU's system clock and reset control register (SCCR).
The control is as follows:
0 = 2.6-V bus signals full drive (50-pF load)
1 = 2.6-V bus signals reduced drive (25-pF load)
2.6.2

Signal State During Reset

While HRESET is asserted, the reset-configuration value is latched from the data bus into
various bits on the part. The function of many signals depends upon the value latched. If
the value on the data bus changes, then the function of various signals may also change.
This is especially true if the reset configuration word (RCW) comes from the Flash, because
the Flash does not drive the RCW until 256 clocks after the start of HRESET. However, the
signals must not cause any spurious conditions or consume an excessive amount of power
during reset. To prevent these conditions, the signals need to have a defined reset state.
Table 25-15 describes the reset state of the signals based on signal functionality.
2-26
PRELIMINARY—SUBJECT TO CHANGE WITHOUT NOTICE
NOTE
MPC533 Reference Manual MOTOROLA