ZiLOG Z80 Handbook page 26

equipment, to mention a few of the virtually dozens of devices.
Some of the more common generic types will be covered in a later
chapter of this section along with special-purpose LSI chips of the
Zilog Z-80 family which are designed to permit ease of interfacing.
The last functional block of Fig. 2-10 is that of the control panel.
Many current microcomputers have dispensed with a control panel
except for one sparsely configured with a power switch and a reset
switch. Pressing the reset switch causes a nonmaskable interrupt
which transfers control to a special monitor program in PROM or
ROM memory. The monitor program allows the user to interrogate
memory locations, change the contents of memory locations, modify
registers, load and save programs on I/O devices and other func-
tions. If a control panel is present, it performs the same functions
as the monitor program by allowing the user to manually address,
examine, and change data in CPU registers and memory. The only
advantage that a control panel would have over a monitor program
is that only the CPU, memory, and control panel are required to
execute programs. However, any viable system must have some kind
of I/O device and in almost all cases, the control panel is an added
complexity.
Section III discusses many of the more popular Z-80 microcom-
puter systems and will give the reader an overview of what is avail-
able in current Z-80 microcomputers insofar as system architecture
is concerned.
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