SWTPC ASCII, Manual

Page: 2 / 12

1
KBD-5 KEYBOARD
General Description
The KBD-5 keyboard and ASCII encoder utilizes a single MOS integrated
circuit to perform the bulk of all necessary operations to generate full 8 bit
parallel ASCII output code complete with a parity bit for error detection.
Debounce is internal and automatic and choice between positive or negative
keypressed output strobe is provided. The keyboard can be programmed for upper
case characters only, or upper and lower case characters. The KBD-5 has the
features of n key lockout and 2 key rollover to help in reducing typing errors.
Once a key is pressed pressing other keys will have no effect until the first
key is released. The KBD-5 is already programmed for the control functions LINE
FEED, RETURN and ESCAPE and can easily be programmed for other control
functions. The keyboard also has two SPST locking keyswitches which can be used
for turning the RECEIVE, TRANSMIT and ECHO functions of a terminal such as the
CT-1024 on and off. The keyboard also has an automatic repeat function which
causes a string of characters to be transmitted after a key has been depressed
for more than about 0.5 seconds.
Assembling your Keyboard and ASCII Encoder
NOTE: MOS integrated circuits are susceptible to damage by static
electricity. Although some degree of protection is provided internally within
the integrated circuits, their cost demands the utmost in care. Before opening
and/or installing any MOS integrated circuits you should ground your body and
all metallic tools coming into contact with the leads through a 1M ohm 1/4 watt
resistor (supplied with the kit). The ground must be an "earth" ground such as a
water pipe, and not the circuit board ground. As for the connection to your
body, attach a clip lead to your watch or metal ID bracelet. Make absolutely
sure you have the 1M ohm resistor connected between you and the "earth" ground,
otherwise you will be creating a dangerous shock hazard. Avoid touching the
leads of the integrated circuits any more than necessary when installing them
even if you are grounded. On those MOS IC's being soldered in place, the tip of
the soldering iron should be grounded as well (separately from your body ground)
either with or without a 1 Meg ohm resistor. Most soldering irons having-a three
prong line cord already have a grounded tip. Static electricity should be an im-
portant consideration in cold, dry environments. It is less of a problem when it
is warm and humid.
( ) Install the 14 jumpers on the PC board. Use some of the light gauge wire
supplied with the kit or excess resistor leads. On the longer jumpers use
insulated wire to keep the jumper from shorting to other components.
Jumpers are denoted on the circuit board by solid lines connecting two
pads. As with all other component installation, unless otherwise noted,
pull the jumpers down flush with the circuit board and solder.
( ) Install the resistors and capacitors on the circuit board using the
component layout on the board and the parts list. Bend the leads over on
the back side of the board and trim so that 1/16" to 1/8" of lead remains.
Solder.
Scanned and edited by Michael Holley Mar 02, 2002 Revised May 23, 2003
Southwest Technical Products Corporation Document Circa 1975