Intel 21555 - Attaching Multiple Devices on the ROM Interface

90 21555 Non-Transparent PCI-to-PCI Bridge User Manual
Parallel ROM Interface
.
Figure 18. Attaching Multiple Devices on the ROM Interface
A7473-01
Other
Device
Selects
Other Device Read Strobe
Other Device Write Strobe
Other Device Data
Other Device Ready Line
21555
pr_ad[7:0]
pr_wr_l
pr_rd_l
pr_cs_l(pr_rdy)
sr_cs sr_cs
sr_ck
sr_di
sr_do
a[20:16]
a[15.8]
a21
a22
a23
a[7:0]
OE#
WE#
d[7:0]
CE#
Parallel
ROM
pr_ad[2]
pr_ad[1]
pr_ad[0]
en
en
en
decoder
en
Serial
ROM
8-bit register
8-bit register
8-bit register
pr_ale_l
pr_clk