ZiLOG Z8 Technical Manual

Reset and Clock
Figure 8-6 shows the recommended circuit configu-
ration for a battery-backed supply system.
Since XTAL2 is replaced by V
MM
, an external
clock generator must be used to input the Z8 clock
via the XTAL1 input.
+ 5 V -------+----1 Vee
TRICKLE
CHARGE~---J~--~r
-=- 3.6 V
I NICAD
Z8
Figure 8-6. Battery-Backed Register Supply
ACCESS NORMAL
ROM AT OOCH
8.4 TEST foIDE
Test mode is a special mode of operation that
facilitates testing of Z8 devices containing
on-board ROM (Z8601 and Z8611). Test mode must
also be used to reset the Z8682. When Test mode is
invoked, an additional on-board ROM is mapped into
the first 64 locations of program memory. Figure
8-7 shows the difference between Normal and Test
modes of operation.
Test mode is entered by driving the RESET input to
a voltage level of VCC + 2.5 V after a normal
Reset cycle (Figure 8-8): This voltage is
absolutely essential for proper opera~ion.
After entering Test mode, instructions are fetched
from the internal test ROM. Port 1 is configured
for Address/Data operation, followed by a JUMP to
external memory location %812 for the Z8601 and
Z8682, or %1012 for the Z8611. Once in external
memory, diagnostic routines, invoked via the
ACCESS TEST
ROM AT OOCH
ON·CHIP
PROGRAM
ROM
%3F .. --------+---------~-------- .. %3F
%OC
USER
ROM
TEST
ROM
%OC
%00 %00
Figure 8-7. Normal and Test Hade Flow
8-4 2037-010,3047-080

ZiLOG Z8 Specifications

General

Brand	ZiLOG
Model	Z8
Category	Desktop
Language	English