Overview
8-2
8.1
Overview
The expansion bus is a 32-bit wide bus that supports interfaces to a variety of
asynchronous peripherals, asynchronous or synchronous FIFOs, PCI bridge
chips, and other external masters.
The expansion bus offers a flexible bus arbitration scheme, implemented with
two signals, XHOLD and XHOLDA. The expansion bus can operate with the
Internal arbiter enabled, in which case any external hosts must request the bus
from the DSP. For increased flexibility, the internal arbiter can be disabled, and
the DSP requests the bus from an external arbiter.
The expansion bus has two major sub blocks—the I/O port and host port inter-
face. A block diagram of the expansion bus is shown in Figure 8–1.
Figure 8–1. Expansion Bus Block Diagram
Expansion bus
XCLKIN
Expansion bus host channel
XFCLK
XD[31:0]
XCE[3:0]
XBE[3:0]/XA[5:2]
XOE
XRE
XWE/XWAIT
XCS
XAS
XCNTL
XW/R
XRDY
XBLAST
XBOFF
XHOLD
XHOLDA
Shared signals
I/O Port:
asynchronous
peripheral/
FIFO interface
Host port interface
Bus arbitration signals
DMA controller