Expansion Bus Host Port Operation
8-29
Expansion Bus
Burst Read Transfer
The timing presented in Table 8–16 can be referenced for a visual description
of the steps required to complete a burst read initiated by the ’C6202 and
throttled by the XWAIT and XRDY signals.
Figure 8–19. Read Transfer Initiated by the TMS320C6202 and Throttled by
XWAIT and XRDY (Internal Bus Arbiter Disabled)
XCLKIN (input)
XHOLD (output)
XHOLDA (input)
XAS (output)
XW/R (output)
XBLAST (output)
XBE[3:0] (output)
XD[31:0] (i/o)
XRDY (input)
XWAIT (output)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
BE
D1
D2 D3 D4
D5
D6
D7
D8
AD
The step by step description of the events marked above the waveforms in
Figure 8–19 follows:
1) The ’C6202 requests the expansion bus by asserting XHOLD output.
2) The DSP waits for the expansion bus.
3) The external bus arbiter asserts the XHOLDA signal, and the ’C6202
starts driving the bus. The XAS, XW/R, XBLAST, XBE[3:0] signals
become outputs, and the XRDY signal becomes an input.
4) Address phase: During this phase, XAS is asserted and the address is
presented on the expansion bus.