MiTAC 7521 PLUS/N service manual Ads#, Aerr#, Bclk, Berr#, Binit#, Bnr#

7521Plus / N N/B MAINTENANCE

5.Pin Descriptions Of Major Components

5.1Pentium III/Celeron FC-PGA2 CPU

Alphabetical Signal Reference

Signal Name	I/O	Signal Description
A[35:3]#	I/O	The A[35:3]# (Address) signals define a 2 36 -byte physical memory
	GTL+	address space. When ADS# is active, these signals transmit the
		address of a transaction; when ADS# is inactive, these signals
		transmit transaction information. These signals must be connected to
		the appropriate pins/balls of both agents on the system bus. The
		A[35:24]# signals are protected with the AP1# parity signal,
		and the A[23:3]# signals are protected with the AP0# parity signal.
		On the active-to-inactive transition of RESET#, each processor bus
		agent samples A[35:3]# signals to determine its power-on
		configuration. See Section 4 of this document and the PentiumII
		Processor Developer’s Manual for details.
A20M#	I	If the A20M# (Address-20 Mask) input signal is asserted, the
	1.5V	processor masks physical address bit 20 (A20#) before looking up a
	Tolerant	line in any internal cache and before driving a read/write transaction
		on the bus. Asserting A20M# emulates the 8086 processor's address
		wrap-around at the 1-Mbyte boundary. Assertion of A20M# is only
		supported in Real mode.
ADS#	I/O	The ADS# (Address Strobe) signal is asserted to indicate the validity
	GTL+	of a transaction address on the A[35:3]# signals. Both bus agents
		observe the ADS# activation to begin parity checking, protocol
		checking, address decode, internal snoop or deferred reply ID match
		operations associated with the new transaction. This signal must be
		connected to the appropriate pins/balls on both agents on the system
		bus.
AERR#	I/O	The AERR# (Address Parity Error) signal is observed and driven by
	GTL+	both system bus agents, and if used, must be connected to the
		appropriate pins/balls of both agents on the system bus. AERR#
		observation is optionally enabled during power-on configuration; if
		enabled, a valid assertion of AERR# aborts the current transaction.
		If AERR# observation is disabled during power-on configuration, a
		central agent may handle an assertion of AERR# as appropriate to the
		error handling architecture of the system.
AP[1:0]#	I/O	The AP[1:0]# (Address Parity) signals are driven by the request
	GTL+	initiator along with ADS#, A[35:3]#, REQ[4:0]# and RP#. AP1#
		covers A[35:24]#. AP0# covers A[23:3]#. 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. This allows parity to be high when
		all the covered signals are high. AP[1:0]# should be connected to the
		appropriate pins/balls on both agents on the system bus.
BCLK	I	The BCLK (Bus Clock) signal determines the system bus frequency.
	2.5V	Both system bus agents must receive this signal to drive their outputs
	Tolerant	and latch their inputs on the BCLK rising edge. All external timing
		parameters are specified with respect to the BCLK signal.

Signal Name	I/O	Signal Description
BERR#	I/O	The BERR# (Bus Error) signal is asserted to indicate an
	GTL+	unrecoverable error without a bus protocol violation. It may be driven
		by either system bus agent and must be connected to the appropriate
		pins/balls of both agents, if used. However, the mobile Pentium III
		processors do not observe assertions of the BERR# signal.
		BERR# assertion conditions are defined by the system configuration.
		Configuration options enable the BERR# driver as follows:
		• Enabled or disabled
		• Asserted optionally for internal errors along with IERR#
		• Asserted optionally by the request initiator of a bus transaction after
		it observes an error
		• Asserted by any bus agent when it observes an error in a bus
		transaction
BINIT#	I/O-	The BINIT# (Bus Initialization) signal may be observed and driven
	GTL+	by both system bus agents and must be connected to the appropriate
		pins/balls of both agents, if used. If the BINIT# driver is enabled
		during the power-on configuration, BINIT# is asserted to signal any
		bus condition that prevents reliable future information.
		If BINIT# is enabled during power-on configuration, and BINIT# is
		sampled asserted, all bus state machines are reset and any data which
		was in transit is lost. All agents reset their rotating ID for bus
		arbitration to the state after reset, and internal count information is
		lost. The L1 and L2 caches are not affected.
		If BINIT# is disabled during power-on configuration, a central agent
		may handle an assertion of BINIT# as appropriate to the Machine
		Check Architecture (MCA) of the system.
BNR#	I/O-	The BNR# (Block Next Request) signal is used to assert a bus stall by
	GTL+	any bus agent that is unable to accept new bus transactions. During a
		bus stall, the current bus owner cannot issue any new transactions.
		Since multiple agents may need to request a bus stall simultaneously,
		BNR# is a wired-OR signal that must be connected to the appropriate
		pins/balls of both agents on the system bus. In order to avoid wire-OR
		glitches associated with simultaneous edge transitions driven by
		multiple drivers, BNR# is activated on specific clock edges and
		sampled on specific clock edges.
BP[3:2]#	I/O	The BP[3:2]# (Breakpoint) signals are the System Support group
	GTL+	Breakpoint signals. They are outputs from the processor that indicate
		the status of breakpoints.
BPM[1:0]#	I/O	The BPM[1:0]# (Breakpoint Monitor) signals are breakpoint and
	GTL+	performance monitor signals. They are outputs from the processor
		that indicate the status of breakpoints and programmable counters
		used for monitoring processor performance.

84