Intel 521 Data Sheet - Page 71

Land Listing and Signal Descriptions Table 4-3. Signal Description (Sheet 6 of 8) Name Type Description PROCHOT# PWRGOOD REQ[4:0]# RESET# RS[2:0]# RSP# SKTOCC# SMI# Input/ Output As an output, PROCHOT# (Processor Hot) will go active when the processor temperature monitoring sensor detects that the processor has reached its maximum safe operating temperature. This indicates that the processor Thermal Control Circuit (TCC) has been activated, if enabled. As an input, assertion of PROCHOT# by the system will activate the TCC, if enabled. The TCC will remain active until the system de-asserts PROCHOT#. See Section 5.2.4 for more details. Input PWRGOOD (Power Good) is a processor input. The processor requires this signal to be a clean indication that the clocks and power supplies are stable and within their specifications. 'Clean' implies that the signal will remain low (capable of sinking leakage current), without glitches, from the time that the power supplies are turned on until they come within specification. The signal must then transition monotonically to a high state. PWRGOOD can be driven inactive at any time, but clocks and power must again be stable before a subsequent rising edge of PWRGOOD. The PWRGOOD signal must be supplied to the processor; it is used to protect internal circuits against voltage sequencing issues. It should be driven high throughout boundary scan operation. Input/ Output REQ[4:0]# (Request Command) must connect the appropriate pins/lands of all processor FSB agents. They are asserted by the current bus owner to define the currently active transaction type. These signals are source synchronous to ADSTB0#. Refer to the AP[1:0]# signal description for a details on parity checking of these signals. Input Asserting the RESET# signal resets the processor to a known state and invalidates its internal caches without writing back any of their contents. For a power-on Reset, RESET# must stay active for at least one millisecond after VCC and BCLK have reached their proper specifications. On observing active RESET#, all FSB agents will de-assert their outputs within two clocks. RESET# must not be kept asserted for more than 10 ms while PWRGOOD is asserted. A number of bus signals are sampled at the active-to-inactive transition of RESET# for power-on configuration. These configuration options are described in the Section 6.1. This signal does not have on-die termination and must be terminated on the system board. Input RS[2:0]# (Response Status) are driven by the response agent (the agent responsible for completion of the current transaction), and must connect the appropriate pins/lands of all processor FSB agents. Input RSP# (Response Parity) is driven by the response agent (the agent responsible for completion of the current transaction) during assertion of RS[2:0]#, the signals for which RSP# provides parity protection. It must connect to the appropriate pins/lands of all processor FSB agents. A correct parity signal is high if an even number of covered signals are low and low if an odd number of covered signals are low. While RS[2:0]# = 000, RSP# is also high, since this indicates it is not being driven by any agent guaranteeing correct parity. Output SKTOCC# (Socket Occupied) will be pulled to ground by the processor. System board designers may use this signal to determine if the processor is present. Input SMI# (System Management Interrupt) is asserted asynchronously by system logic. On accepting a System Management Interrupt, the processor saves the current state and enter System Management Mode (SMM). An SMI Acknowledge transaction is issued, and the processor begins program execution from the SMM handler. If SMI# is asserted during the de-assertion of RESET#, the processor will tristate its outputs. Datasheet 71