Digi NS9750 - Manual (Page 429)

w w w . d i g i e m b e d d e d . c o m 4 0 5
P C I - t o - A H B B r i d g e
PCI-to-AHB bridge functionality
Figure 71 shows the PCI-to-AHB bridge. Downstream transactions are those initiated
on the AHB bus; upstream transactions are those initiated on the PCI bus.
Figure 71: PCI-to-AHB bridge diagram
AHB master interface
The AHB master interface block controls the bridge’s access to the AHB bus as a
master, and is used for reads and writes to the AHB bus that are initiated on the PCI
bus by an external PCI bus master. The requests are transferred to the AHB master
from the PCI target interface. PCI writes are posted in the dual 64-byte PCI target
write buffer. AHB read data is stored in the 64-byte AHB master read buffer before
PCI target
PCI target
write buffer
32x32
PCI bus
arbiter
PCI/Bridge
Config &
Status
registers
AHB master
AHB master
read buffer
16x32
AHB slave/
target
AHB target
write buffer
32x32
PCI master
read buffer
16x32
PCI master
write buffer
32x32
PCI master
Downstream
Upstream
Bus/
Req
grant
Interrupt
Note: The PCI Bus arbiter is not part
of the bridge. It is a separate module
shown here for illustration. It's use is
optional.
PCI
bu
s
AH
B bus