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The display: segment data, grid signal information and
* keyboard strobe data are the output of the CPU via
the DO ~ D7 lines,
—
Thé segment data being sent to the segment latch
— The keyboard strobe and grid signal information be-
ing sent to the 4-16 decoder". The strobing output
-of the "4-16 decoders" are used for strobing both the
keyboard and the display. grid signals.
The strobing output
of the "4-16
decoders" are sent
thru an inverter and are now known as the keyboard and
mode switch strobe signals KSO ~ KS7.
The KRO to KR®5 signals are the keyboard and mode
. 'switch return signals for the CPU.
~
— These signals are sent to a 3-state. buffer.
— The 3-state buffer .is enabled when the KRS signal is
"issued low.
— When the 3-state buffer is enabled, the KRO ~ KR5
information is allowed.to pass through to the CPU. for
reading,
FOR
FURTHER
DETAILED
EXPLANATION
OF KEY-
BOARD
AND
MODE
SWITCH
READ
FOR
DISPLAY
CONTROL OPERATION, REFER TO CHAPTER 9-2 AND
CHAPTER
9-3
OF
THE
"CASH
REGISTER
BASIC
MANUAL".
5-8. Buzzer circuit
+5V
Buzzer
(Speaker)
@
@—
Cc
LEE
0.47 uF
50V
*: Oper collector
output type
Oscillator circuit
The resistor (R) and the capacitor (C) in combination with
the schmidt trigger will produce an oscillation at point (@).
This oscillation will appear at the output of the schimidt
trigger as a square wave. at-point ® » See-Fig. 11,
TL7V
Point @)
0.9V
Point ®
Fig. 11
RES (reset) signal is usually: at a low-level except when the
power is turned on or off.
:
When the buzzer signal (BZ) goes low level, inverted pulse
of OS (point ©) ) will appear at point ©) (the base of 08)
turning on and off O8.
This will result in the Buzzer sounding.
Point ©
0.7
|
Point @
o
sv I
f
| |
|
Fig. 12
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