Hardware Implementation Examples - ZiLOG Z80-CPU Technical Manual

9.0 HARDWARE IMPLEMENTATION EXAMPLES
This chapter is intended to serve as a basic introduction to implementing systems with the Z8D-CPU.
MINIMUM SYSTEM
Figure 9.D·l is a diagram of a very simple Z·8D system. Any Z-8D system must include the following
five elements:
1) Five volt power supply
2) Oscillator
3) Memory devices
4) I/O circuits
5) CPU
AO-Ag
+5V GND
ADDRESS
IN
MREO
CE l .
8KBIT
RD
CE 2
ROM
+5V
Z80
DATA BUS
CPU
lORa
r
AO
Ml
Al
OUTPUT INPUT
DATA DATA
FIGURE 9.0-1
MINIMUM Z80 COMPUTER SYSTEM
Since the Z8D-CPU only requires a single 5 volt supply, most small systems can be implemented using
only this single supply.
The oscillator can be very simple since the only requirement is that
it
be a 5 volt square wave. For
systems not funning at full speed, a simple RC oscillator can be used. When the CPU is operated near the
highest possible frequency, a crystal oscillator is generally required because the system timing will not
tolerate the drift or jitter that an RC network will generate. A crystal oscillator can be made from inverters
and a few discrete components or monolithic circuits are widely available.
The external memory can be any mixture of standard RAM, ROM, or PROM. In this simple example
we have shown a single 8K bit ROM (lK bytes) being utilized as the entire memory system. For this
example we have assumed that the Z-8D internal register configuration contains sufficient Read/Write
storage so that external RAM memory is not required.
59