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DATA SHEET
PM7367 FREEDM-32P32
ISSUE 2
PMC-1991499
FRAME ENGINE AND DATA LINK MANAGER
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMER’S INTERNAL USE
288
During Clock 5, the target places the second data word onto the AD[31:0] bus
and drives TRDYB to indicate to the initiator that the data is valid.
During Clock 6, the initiator latches the second data word and negates IRDYB to
indicate to the target that it is not ready for the next transfer. The target shall
drive the third data word until the initiator accepts it.
During Clock 7, the initiator asserts IRDYB to indicate to the target it is ready for
the third data word. It also negates FRAMEB since this shall be the last transfer.
During Clock 8, the initiator latches in the last word and negates IRDYB. The
target, having seen FRAMEB negated in the last clock cycle, negates TRDYB
and DEVSELB. All of the above signals shall be driven to their inactive state in
this clock cycle, except for FRAMEB which shall be tri-stated. The target shall
stop driving the AD[31:0] bus and the initiator shall stop driving the C/BEB[3:0]
bus; this shall be the turnaround cycle for these signals.
Figure 28 – PCI Read Cycle
PCICLK
FRAMEB
AD[31:0]
C/BEB[3:0]
1
2
3
4
5
6
7
8
9
IRDYB
TRDYB
DEVSELB
T
Address
Data 1
Data 2
Data 3
Byte Enable
Byte Enable
Byte Enable
Bus Cmd
T
T
T
T
T
T
A PCI burst write transaction is shown in Figure 29. The cycle is valid for target
and initiator accesses. The target is responsible for incrementing the address for
the duration of the data burst. The 'T' symbol stands for a turn around cycle. A
turn around cycle is required on all signals which can be driven by more than one
agent.
During clock 1, the initiator drives FRAMEB to indicate the start of a cycle. It also
drives the address onto the AD[31:0] bus and drives the C/BEB[3:0] lines with
the write command (in the above example the command would indicate a burst
write). The IRDYB, TRDYB and DEVSELB signals are in turnaround mode (no