IBM PowerPC 604 User Manual page 304

State Meaning Asserted-The 604 initiates a machine check interrupt operation if
MSR[EE] and HIDO[EMCP] are set; if MSR[EE] is cleared and
HIDO[EMCP] is set, the 604 must terminate operation by internally
gating off all clocks, and releasing all outputs (exceptCKSTP _OUT)
to the high impedance state. If HIDO[EMCP] is cleared, the 604
ignores the interrupt condition. The MCP signal must be held
asserted for two bus clock cycles.
Negated-Indicates that normal operation should proceed. See
Section 8.8.1, "External Interrupts."
Timing Comments Assertion-May occur at any time and may be asserted
asynchronously to the input clocks. The MCP input is negative edge-
sensitive.
Negation-May be negated two bus cycles after assertion.
If deterministic cycle sequencing is required (for example, in multiple processor systems
operating in lock step), the MCP signal should be asserted and negated synchronously with
the SYSCLK signal.
7.2.9.4 Checkstop lnput(CKSTP _IN)-lnput
The checkstop input (CKSTP _IN) signal is input only on the 604. Following are the state
meaning and timing comments for the CKSTP _IN signal.
State Meaning Asserted-Indicates that the 604 must terminate operation by
internally gating off all clocks, and release all outputs (except
CKSTP _OUT) to the high impedance state. Once CKSTP _IN has
been asserted it must remain asserted until the system has been reset.
Negated-Indicates that normal operation should proceed. See
Section 8.8.2, "Checkstops."
Timing Comments Assertion-May occur at any time and may be asserted
asynchronously to the input clocks.
Negation-May occur any time after the CKSTP _OUT output signal
has been asserted.
7.2.9.5 Checkstop Output (CKSTP _OUT)-Output
The checkstop (CKSTP _OUT) signal is output only on the 604. Note that the
(CKSTP _OUT) signal is an open-drain type output, and requires an external pull-up
resistor (for example, 10 W
to
Vdd) to assure proper deassertion of the (CKSTP _OUT)
signal. Following are the state meaning and timing comments for the CKSTP _OUT signal.
State Meaning Asserted-Indicates that the 604 has detected a checkstop condition
7-26
and has ceased operation.
Negated-Indicates that the 604 is operating normally.
See Section 8.8.2, "Checkstops."
PowerPC 604 RISC Microproceeaor User's Manual