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 |
| 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 |
| 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 |
| 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 |
| 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. |