
2-28
PowerPC Microprocessor Family: The Bus Interface for 32-Bit Microprocessors
2.9.3 Machine Check Interrupt (MCP)—Input
Following are state and timing descriptions for the machine check interrupt (MCP) input
signal. This signal is not on the 601.
State Meaning
Asserted—The processor initiates a machine check interrupt
operation if MSR[ME] and HID0[EMCP] are set; if MSR[ME] is
cleared and HID0[EMCP] is set, the processor must terminate
operation by internally gating off all clocks and releasing all outputs
(except CKSTP_OUT) to the high-impedance state. If HID0[EMCP]
is cleared, the processor ignores the interrupt condition. The MCP
signal must remain asserted for two bus clock cycles.
Negated—Normal operation should proceed.
Assertion—May occur at any time and may be asserted
asynchronously to the input clocks. MCP is negative edge-sensitive.
Negation—May be negated two bus cycles after assertion.
Timing Comments
2.9.4 Checkstop Input (CKSTP_IN)—Input
Following are state and timing descriptions for the checkstop input signal (CKSTP_IN).
State Meaning
Asserted—The processor must terminate operation by internally
gating off all clocks and releasing all outputs except CKSTP_OUT
to high-impedance state. Once asserted, CKSTP_IN must remain
asserted until the system has been reset.
Negated—Normal operation should proceed. See Section 5.3,
“Machine Check and Checkstops.”
Timing Comments
Assertion—May occur at any time and may be asserted
asynchronously to the input clocks.
For the 601, CKSTP_IN must be asserted at least three PCLK_EN
clock cycles. Or it may be asserted synchronously meeting setup and
hold times (specified in the hardware specifications) and must be
asserted for at least two PCLK_EN clock cycles.
Negation—May occur any time after CKSTP_OUT is asserted.
2.9.5 Checkstop Output (CKSTP_OUT)—Output
Following are state and timing descriptions for checkstop output (CKSTP_OUT) as an
output signal. Note that CKSTP_OUT is an open-drain type output and requires an external
pull-up resistor to assure proper deassertion.
State Meaning
Asserted—The processor detected a checkstop condition and ceased
operation.
Negated—The processor is operating normally. See Section 5.3,
“Machine Check and Checkstops.”