Here is the recommended setup for standalone testing of the front panel, just to make sure it is the correct start.
-J2 Pin 9 [/out] is connected to 3 components. 0.1uF cap other end ground, momentary switch other end ground, 100K resistor other end Vcc(5V). Original recommendation was to use J2 Pin 8, however (b)TTL option that pin is not connected to anything but P1 TX 5.
-J2 Pin 24 -CLOCK- high (Vcc) or low (Ground)
-P1 1 ground to (-) power supply
-J2 P19 Vcc to +5V power supply
> I cannot get S8 work no matter what. While running FFF1 sequence it is using 92mA current at 5V supply.
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OK, that's correct. You have enough 5v power.
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> While testing with the logic probe, 74LS145 inputs to A(15), B(14) and C(13) are fine but D(12) is always LOW.
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That's also correct. 74LS145 input D (pin 12) is always low when the interrupt handler is working. The inputs to it count from 0-7 and repeat. If the Z80 interrupt handler fails to respond to the keyboard/display interrupt, then input D (pin 12) goes high to disable the LED display and keypad.
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As I described earlier, you can test the Front Panel by itself, without the CPU board. You should be able to set the A B C inputs of the 74LS145 (with the 74HC393 counter) to each of the 8 states, then operate each keypad key in turn, and see the IN bits identify which key you pressed.
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Lee
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I am using the (b) TTL configuration both on the Z80 card as well as the Front panel.
--
Excellence does not require perfection. -- Henry James
But it *does* require attention to detail! -- Lee Hart
--
Lee A. Hart
Kerem Kapkin