CPC700 User’s Manual—Preliminary
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transfer the data before it may assert Sl[x]_AddrAck. If the address is to PCI I/O or memory, the bridge
immediately posts the write if there is sufficient buffer space. All posted writes must be flushed before a
read initiated by a PLB master is allowed to complete. Writes to PCI configuration space or PCI Special
Cycle are not posted.
Internal configuration writes are not allowed to execute if posted write data exists in either write buffer. The
internal configuration mechanism is described in Section 5.9 “Bridge Configuration” .
5.7.3.1 PLB Slave Write Post Buffer
The PCI interface has a write post buffer that may contain two separate PLB write transactions. New PLB
write requests are rearbitrated if there is not enough room in the write post buffer. (Note that in the
CPC700, the CPU interface logic also contains a two-entry, write post buffer. Thus a total of four writes can
be posted between the CPU and the PCI bus.)
The buffers are not snooped, and are always completed on the PCI bus in the same order as they are
received on the PLB bus.
5.7.4 PLB Request Responses (CPU to PCI Transactions)
Table 44. describes the PCI interface’s response to PLB master requests. The PCI terms “retry” and “dis-
connect” refer to, respectively, transaction abort with no data transferred and transaction abort with at least
one beat of data transferred. A blind disconnect refers to one in which a PCI target disconnects concur-
rently with the bridge’s last PCI data beat.
All actions listed in the “PCI Interface Actions” column are done in sequential order. The table assumes that
the PCI interface is initially in the idle state and has available buffer space. See Table 12 on page 3-10.
Table 44.PCI interface Responses to PLB Requests
PLB Direction
and Size
PCI Address
Space
PLB, PCI Bus
Action
PCI Response
PCI interface Action
read, 1-4 byte
(CPU to PCI
read)
memory, I/O
configuration or
int. ack.
PLB: assert hold
PCI Bus
Sl[x]_wait
PCI: request bus
retry
rearbitrate PLB trans-
action
read, 1-4 byte
memory, I/O
configuration or
int. ack.
PLB: assert
Sl[x]_wait
PCI: request bus
accept or blind
disconnect
accept read data;
assert AddrAck; com-
plete data tenure
read, 1-4 byte
memory, I/O
configuration or
int. ack.
PLB: assert
Sl[x]_wait
PCI: request bus
target/master
abort
deassert Sl[x]_wait.
assert sl[x]_Merr(x)
read line, any
size
memory I/O,
configuration or
int. ack.
PLB: none (not sup-
ported)
PCI: none
n/a
none
Summary of Contents for CPC700
Page 10: ...Table of Contents x Table of Contents...
Page 16: ...Tables xvi List of Tables...
Page 28: ...1 12 CPC700 User s Manual Preliminary...
Page 72: ...3 36 Processor Interface...
Page 132: ...4 60 Memory Controller...
Page 184: ...5 52 PCI Interface...
Page 194: ...6 10 Clock Power Management and Reset...
Page 224: ...8 18 IIC...
Page 244: ...10 10 Interrupt Controller...
Page 246: ...I 11 2 JTAG...
Page 250: ...12 4 Processor Local Bus PLB...
Page 262: ...14 10 Register Summary...
Page 267: ...CPC700 User s Manual Preliminary...