Zilog Z16C35 User Manual
Page 177
Application Note
Interfacing Z80
®
CPUs to the Z8500 Peripheral Family
6
A SIMPLE Z80-Z8500 SYSTEM
The Z8500 devices interface easily to the Z80 CPU, thus
providing a system of considerable flexibility. Figure 16
illustrates a simple system using the Z80A CPU and Z8536
Counter/Timer and Parallel I/O Unit (CIO) in a mode 1 or
non-interrupt environment. Since interrupt vectors are not
used, the /INTACK line is tied High and no additional logic
is needed. Because the CIO can be used in a polled
interrupt environment, the /INT pin is connected to the
CPU. The Z80 should not be set for mode 2 interrupts
since the CIO will never place a vector onto the data bus.
Instead, the CPU should be placed into mode 1 interrupt
mode and a global interrupt service routine can poll the
CIO to determine what caused the interrupt to occur. In this
system, the software emulation procedure described
above is effective.
Additional Information in Zilog Publications:
The Z80 Family User’s Manual includes technical
information on the Z80 CPU, DMA, PIO, CTC, and SIO.
Technical information on the Z80 CPU AC Characteristics
and the Z80 Family Interrupt Structure Tutorial can be
found in the Z80 Databook.
The Z8000 User’s Manual features technical information
on the Z8536 CIO and Z8038 FIO.
Figure 16. Z80 to Z8500 Simple System Mode 1 Interrupt or Non-Interrupt Structure
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