
MOTOROLA
Chapter 8. Signal Descriptions
8-41
Signal Descriptions
Negation—May be negated two bus cycles after assertion.
8.3.9.5
Checkstop Signals
There is both an checkstop input and checkstop output signal on the G2 core. The core also
implements checkstop output enable and checkstop high-impedance enable signals.
8.3.9.5.1
Checkstop Input (core_ckstp_in)
Following are the state meaning and timing comments for core_ckstp_in.
State Meaning
Asserted—Indicates that the core must terminate operation by
internally gating off all clocks, and releasing all outputs (except
core_ckstp_out) to the high-impedance state. Once core_ckstp_in is
asserted, it must remain asserted until the system has been reset.
Negated—Indicates that normal operation should proceed. See
Section 9.7.2, “Checkstops.”
Timing Comments
Assertion—May occur at any time and may be asserted
asynchronously to the input clocks.
Negation—May occur anytime after core_ckstp_out is asserted.
8.3.9.5.2
Checkstop Output (core_ckstp_out)
The core_ckstp_out signal is output only on the G2 core. The core also implements
checkstop output enable and checkstop high-impedance enable signals. core_ckstp_out
acts as follows:
If core_ckstp_tre is asserted, the output is in one of the following three states—high
impedance, driven high, or driven low.
If core_ckstp_tre is negated, the output is either driven to the high or low state. In
this case, a valid value on core_ckstp_out exists when core_ckstp_oe is asserted.
Following are the state meaning and timing comments for the core_ckstp_out output.
State Meaning
Asserted—Indicates that the core has detected a checkstop condition
and has ceased operation.
Negated—Indicates that the core is operating normally. See
Section 9.7.2, “Checkstops.”
Timing Comments
Assertion—May occur at any time and is asserted asynchronously to
core_sysclk.
Negation—Is negated upon assertion of core_hreset.
High Impedance—Occurs after the negation of core_ckstp_oe, if
core_ckstp_tre is asserted. If core_ckstp_tre is negated,
core_ckstp_out is always driven.
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