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3
J5
This connection may be used for the level conversion for a secondary serial port. The TI and TO connections
are the TTL input and output to/from the level converter while the 2I and 2O connections are the RS-232 level
input and output. The picture on the preceding page shows the supplied SIP socket strip is installed in this
connection. This facilitates connection by inserting wires (24 ga. maximum) into the sockets.
Required Components
The components required to support a 28-pin ZX device are listed in the table below. Note that three of the
components are not mounted on the circuit board – one 100nF capacitor, one 10nF capacitor and the inductor.
Quantity
Description
Component Designators
1
ST232A RS-232 level converter
U1
1
Crystal, 14.7456MHz, 18pF
X1
1
Transistor, NPN, 2N3904
Q1
6
Resistor, 10K ohm, ¼ watt
R1, R2, R3, R4, R5, R6
2
Capacitor, ceramic, 27pF
C1, C2
5
Capacitor, ceramic, 100nF
C3, C4, C5, C6
2
Capacitor, ceramic, 10nF
C7
1
Inductor, 10uH, 200mA
Assembly Procedure
The assembly sequence isn’t critical so you may perform the steps in any convenient order. Note carefully the
orientation marks for the ICs. Pin 1 of each has a square pad while the remaining ones are round.
All six resistors are the same value – 10K. The inductor, which looks similar to a resistor, is not mounted on the
board. Rather, it is connected between +5 supply and pin 20 of the ZX-328n as shown in the photo on the
previous page.
There are three different capacitor values in the kit. C1 and C2 are 27pF capacitors. They are marked simply
with “27”. C3 through C6 are 100nF capacitors, marked with “104”. C7 is a 10nF capacitor, marked with “103”.
The remaining two capacitors, one 100nF and one 10nF, are filtering capacitors should be connected directly
across pins of the ZX-328n on your breadboard as shown in the photo on the preceding page. The 100nF
should be connected between pins 20 and 22 and the 10nF should be connected between pins 21 and 22. Pin
22 should also be grounded.
The transistor Q1 must be installed with its flat face toward the edge of the board. The crystal, X1, may be
installed in either orientation.
If you plan to solder square pins to the board to connect the Module to a solderless breadboard, the simplest
way to get them mounted squarely is to insert the square pins for J1, J2 and J3/J4 into the solderless
breadboard and then place the board over the pins and solder them in place. This ensures that the pins are not
misaligned. Whether you use J3 or J4 depends on how you configure the power and ground busses on your
solderless breadboard but only one of them should be connected.
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