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System Controller: PCI Bus Control Signals
PmPPC7448 User’s Manual 10006757-02
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C/BE[7:4]*: BUS COMMAND and BYTE ENABLES During the address phase, the actual bus command is
transferred, otherwise these bits are reserved. During a data phase the lines are used as
byte enables.
CLK: CLOCK This input signal to PPMC modules provides timing for PCI transactions.
DEVSEL*: DEVICE SELECT This sustained three-state signal indicates when a device on the bus has
been selected as the target of the current access.
EREADY: READY This signal is an input for Monarch modules and an output for non-Monarch mod-
ules. It indicates that all modules are initialized and the PCI bus is ready to be enumerated.
FRAME*: CYCLE FRAME This sustained three-state signal is driven by the current master to indicate
the beginning of an access, and continues to be asserted until the transaction reaches its
final data phase.
GNT*: GRANT This three-state signal indicates that access to the bus has been granted to a par-
ticular master. Each master has its own GNT*.
IDSEL: INITIALIZATION DEVICE SELECT This input signal acts as a chip select during configuration
read and write transactions.
INTA*, INTB*, INTC*, INTD*:
PMC INTERRUPTS A, B, C, D These open drain lines are used by the PPMC module to inter-
rupt the baseboard, or vice versa.
IRDY*: INITIATOR READY This sustained three-state signal indicates that the bus master is ready
to complete the data phase of the transaction.
M66EN: ENABLE 66 MHZ This signal indicates to a device whether the bus segment is operating at
66 or 33 MHz in conventional PCI.
MONARCH*: MONARCH When this signal is grounded, it indicates that the PPMC module is a Monarch
and must provide PCI bus enumeration and interrupt handling.
PAR: PARITY This is even parity across AD[31:00] and C/BE[3:0]*. Parity generation is required
by all PCI agents. This three-state signal is stable and valid one clock after the address
phase, and one clock after the bus master indicates that it is ready to complete the data
phase (either IRDY* or TRDY* is asserted). Once PAR is asserted, it remains valid until one
clock after the completion of the current data phase.
PAR64: PARITY UPPER DWORD This three-state signal is the even parity bit that protects
AD[63:32] and C/BE[7:4]*.
PERR*: PARITY ERROR This sustained three-state line is used to report data parity errors during all
PCI transactions except a Special Cycle.