IBM 750GL, 750GX 7.2.9.4 Checkstop Input (CKSTP_IN)—Input, 7.2.9.3 Machine-CheckInterrupt (MCP)—Input, 7.2.9.5 Checkstop Output (CKSTP_OUT)—Output

User’s Manual

IBM PowerPC 750GX and 750GL RISC Microprocessor

7.2.9.3 Machine-Check Interrupt (MCP)—Input

State	Asserted	The 750GX 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
		750GX 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 750GX ignores the interrupt condition. The MCP
		signal must be held asserted for two bus clock cycles.
	Negated	Indicates that normal operation should proceed.
Timing	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.

7.2.9.4 Checkstop Input (CKSTP_IN)—Input

State	Asserted	Indicates that the 750GX must enter the checkstop state and terminate oper-
		ation. The 750GX will internally gate off all clocks and remain in this state
		while CKSTP_IN is asserted. The 750GX will also release all outputs (except
		CKSTP_OUT) to the high-impedance state. CKSTP_IN is not maskable.
		Once CKSTP_IN has been asserted it must remain asserted until the system
		has been reset.
	Negated	Indicates that normal operation should proceed.
Timing	Assertion	May occur at any time and may be asserted asynchronously to the input
		clocks.
	Negation	May occur any time after the	CKSTP_IN	output has been asserted.

7.2.9.5 Checkstop Output (CKSTP_OUT)—Output

Note that the CKSTP_OUT signal is an open-drain type output, and requires an external pull-up resistor (for example, 10 kΩ to VDD) to assure proper deassertion of the CKSTP_OUT signal.

State	Asserted	Indicates that a checkstop condition has been detected, and the processor
		has ceased operation.
	Negated	Indicates that the processor is operating normally.
Timing	Assertion	Might occur at any time and can be asserted asynchronously to input clocks.
	High	Requires	HRESET.
	Impedance

Note: CKSTP_OUT operates as an open-drain output. It will either be in the asserted or high-impedance state.

gx_07.fm.(1.2)	Signal Descriptions
March 27, 2006	Page 271 of 377