Zilog Z08470 - Manual (Page 180)

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UM008101-0601 Direct Memory Access
Bus Release on Match
When the DMA is programmed to stop (release the bus) on match in Burst
or Continuous modes, a match causes BUSREQ to go inactive on the next
DMA operation, for example, at the end of the next read in search-only,
simultaneous transfer/searches, or at the end of the following write in
sequential transfer or transfer/searches (Figure 68).
Figure 68. Bus Release on Match (Burst and Continuous Modes)
Because of the pipelining scheme, matches are determined while the next
DMA read or write is being performed. Table 12 lists the number of bytes
transferred in any class or mode.
The RDY line can go inactive after the matching operation begins without
affecting this bus-release timing. However, the time at which RDY goes
inactive can affect the number of bytes transferred, as described in Table 11
and Figure 32.
Bus Release on Not Ready
Burst mode, when RDY goes inactive, causes BUSREQ to go High on the
next rising edge of CLK after the completion of its current byte operation,
for example, at the end of the current read in search-only, simultaneous
transfer/search, or at the end of the following write in sequential transfer/
BUSREQ
RDY
Byte n DMA
Inactive Read in
Byte n+1
and
on Byte n
Read in
Match Found
Active
Inactive
CLK