MOTOROLA
Chapter 2. Signal Descriptions
2-39
Negated—Indicates that the PCI initiator needs to wait before the
MPC106, acting as a PCI target, can complete the current data phase.
During a read, the MPC106 negates TRDY to insert a wait cycle
when it cannot provide valid data to the initiator. During a write, the
MPC106 negates TRDY to insert a wait cycle when it cannot accept
data from the initiator.
2.2.5.13.2 Target Ready (TRDY)—Input
Following is the state meaning for TRDY as an input signal.
State Meaning
Asserted—Indicates another PCI target is able to complete the
current data phase of a transaction.
Negated—Indicates a wait cycle from another target.
2.2.5.14 PCI Sideband Signals
The PCI specification loosely defines a sideband signal as any signal not part of the PCI
specification that connects two or more PCI-compliant agents, and has meaning only to
those agents. The MPC106 implements four PCI sideband signals—FLSHREQ,
ISA_MASTER, MEMACK, and PIRQ.
2.2.5.14.1 Flush Request (FLSHREQ)—Input
The flush request (FLSHREQ) signal is an input signal on the MPC106. Following is the
state meaning for the FLSHREQ input signal.
State Meaning
Asserted—Indicates that a device needs to have the MPC106 flush
all of its current operations. FLSHREQ should be asserted when
MEMACK is negated and before FRAME is asserted.
Negated—Indicates normal operation for the MPC106. FLSHREQ
should be deasserted after FRAME is deasserted.
2.2.5.14.2 ISA Master (ISA_MASTER)—Input
The ISA master (ISA_MASTER) signal is an input signal on the MPC106. This signal is
only valid for address map A; it has no meaning for address map B or for the emulation
mode address map. Following is the state meaning for the ISA_MASTER input signal.
State Meaning
Asserted—Indicates that an ISA master is requesting system
memory. The ISA_MASTER signal is an implied address bit 31 for
ISA devices that cannot drive a full 32-bit address. Accordingly,
when the MPC106 detects ISA_MASTER asserted, it automatically
asserts DEVSEL. Note that due to the automatic assertion of
DEVSEL when ISA_MASTER is asserted, possible bus contention
can occur if the current transaction is not truly intended for the
MPC106 (or system memory behind it).
Negated—Indicates that no ISA master requires system memory.