Intel ECB-865 user manual Arbitration, Error Reporting

User’s Manual

3.11.38.4Arbitration

REQ#	Request indicates to the arbiter that this agent desires use of the bus. This is a point
	to point signal. Every master has its own REQ# which must be tri-stated while RST#
	is asserted.
GNT#	Grant indicates to the agent that access to the bus has been granted. This is a point
	to point signal. Every master has its own GNT# which must be ignored while RST# is
	asserted.

3.11.38.5Error Reporting

PERR#	Parity Error is only for the reporting of data parity errors during all PCI transactions
	except a Special Cycle. The PERR# pin is sustained tri-state and must be driven
	active by the agent receiving data two clocks following the data when a data parity
	error is detected. The minimum duration of PERR# is one clock for each data phase
	that a data parity error is detected. (If sequential data phases each have a data parity
	error, the PERR# signal will be asserted for more than a single clock.) PERR# must
	be driven high for one clock before being tri-stated as with all sustained tri-state
	signals. There are no special conditions when a data parity error may be lost or when
	reporting of an error may be delayed. An agent cannot report a PERR# until it has
	claimed the access by asserting DEVSEL# (for a target) and completed a data phase
	or is the master of the current transaction.
SERR#	System Error is for reporting address parity errors, data parity errors on the Special
	Cycle command, or any other system error where the result will be catastrophic. If an
	agent does not want a non-maskable interrupt (NMI) to be generated, a different
	reporting mechanism is required. SERR# is pure open drain and is actively driven for
	a single PCI clock by the agent reporting the error. The assertion of SERR# is
	synchronous to the clock and meets the setup and hold times of all bused signals.
	However, the restoring of SERR# to the deasserted state is accomplished by a weak
	pullup (same value as used for s/t/s) which is provided by the system designer and
	not by the signaling agent or central resource. This pullup may take two to three
	clock periods to fully restore SERR#. The agent that reports SERR#s to the
	operating system does so anytime SERR# is sampled asserted.

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