Zenith Z-100 PC series Service Manual page 104

Page
4-18
Detailed Circuit Description
II)
Table 4-6 (continued):
PIN SIGNAL
NUMBER NAME
45 RSTI
46
050SC
47
JMPR*
48 180SC
49 I50SC
50 VDD
51 080SC
52
VSS
53 8M/5M*
54
PB6*
55 SPKR*
56 - 60 BD3-BD7
61 CAS
Gate Array Signals
DESCRIPTION
Used to initiate powerup sequence,
based on charging of capacitor (C2IO)
when system is switched on.
Connection, with pin 49, to 14.31818
MHz oscillator (Y202).
Enables the outputs of drivers so that
the settings of DIP switches (SW202)
can be read.
Connection, with pin 51, to 24.000
MHz oscillator (Y20 1).
Connection, with pin 46, to 14.31818
MHz oscillator (Y202).
+5 VDC.
Connection, with pin 48, to 24.000
MHz oscillator (Y201).
Ground.
Input from dual D flip-flop (U254)
determining clock frequency based
on position of pushbutton switch
(SW201).
Used to disable the keyboard clock.
Signal to speaker via connector (P20 1).
Data outputs (refer also to pins 18 ­
20).
Column address strobes to RAM banks
0,1, and 2.