Figure 66. bus release in byte mode, Figure 67. bus release on end-of-block (burst and, Continuous modes) – Zilog Z08470 User Manual
Page 179: Bus release on end-of-block
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Figure 66.
Bus Release in Byte Mode
The next bus request for the next byte comes after both BUSREQ and BAI
have returned High. In a Z80 environment, BAI returns High one clock
cycle after BUSREQ returns High.
Bus Release on End-of-Block.
When the DMA is programmed to stop on end-of-block in Burst or Contin-
uous modes, an end-of-block causes BUSREQ to go High (inactive) on the
same rising edge of CLK in which the DMA completes the data block
transfer (see Figure 67). The last byte in the block is transferred even if
RDY goes inactive before completion of the last byte operation.
Figure 67.
Bus Release on End-of-Block (Burst and Continuous Modes)
BUSREQ
DMA Active
BAI
CLK
DMA Inactive
BUSREQ
RDY
Current Byte
Operation
DMA
Inactive
Active
Inactive