Pin description, Table 10, Events and actions – Zilog Z08470 User Manual
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Direct Memory Access
PIN DESCRIPTION
The following pin descriptions detail the function of the Z80 DMA external
pins as illustrated in Figure 25 through Figure 28.
A15-A0
System Address Bus (output, tristate). Addresses generated by the DMA are
sent to both source and destination ports, either of which may be main
memory or I/O peripherals.
Table 10. Events and Actions
Event
Actions Possible When Event
Occurs
End-of-Block
1. Release Bus
2. Interrupt CPU
3. Auto Restart
Byte Match (Compare)
1. Release Bus
2. Interrupt CPU
3. Continue
Pulse-control byte matches lower part of
byte counter
1. Generate Pulse
READY Inactive
1. Release Bus
2. Suspend (continuous mode
only)
READY Active
1. Request Bus
2. Interrupt CPU
RETI Instruction (return from interrupt
instruction from the Z80 CPU)
1. Request Bus