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Changes between Revision 3 and Revision 4 Boards
•
Addition of expansion connectors
•
Removal of reverse current protection diode
•
Reset circuit was replaced by a single part which also does power-on reset
•
Larger circuit board with many parts moved around
Connectors and Switches
There aren’t a whole lot of switches and connectors, but the few deserve some
explanation.
J1 – POWER
This is the power input jack. This feeds the 5 volt regulator so while supplies as
high as 12 volts could be used, we really recommend 7.5 to 9 volts maximum so as
not to overheat the regulator. The center pin is positive, outer sleeve is negative.
There is a diode to protect the board from incorrect polarity.
S1 – Power
This is the main power on/off switch. No further explanation is necessary. Note
that the USB interface chip derives power from the main PC, so the power switch
does not turn off the USB interface.
SW2
This selects the input/output device. Normal KIM mode is to have it in the KBD
position which means the LEDs and the keyboard are the “console” for the KIM.
This is the normal mode for a KIM-1.
When the switch is set to TTY then the monitor will use the external terminal (USB)
as the console. Remember when you first choose TTY that you’ll need to press RS
(the red button) and then hit RETURN on your terminal so the monitor can measure
the baud rate. Typically baud rates of 4800 or less work best.
SW3 – VECTORS
The 6502 has three interrupt vectors: RESET, NMI and IRQ. On the KIM they all
default to pointing to code in the KIM monitor, but our board allows you to use
vectors in the KIM EPROM or the expansion EEPROM.
This switch is normally set to the KIM position.
