Click here for a list of the parts required to build an SC102, v1.1, Z80 CTC Module.
Experienced builders can just go ahead and populate the board. There shouldn’t be any surprises to catch you out.
This guide assumes you are familiar with assembling circuit boards, soldering, and cleaning. If not, it is recommended you read some of the guides on the internet before continuing.
First check you have all the required components, as listed in the parts list.
Before assembling it is worth visually inspecting the circuit board for anything that looks out of place, such as mechanical damage or apparent manufacturing defects.
If you have a multimeter that measures resistance or has a continuity test function, check there is not a short on the power supply tracks. Connect the probes to each terminal of one of the capacitors, such as C1. This should be an open circuit, not a short.
The picture below shows what a completed SC102 Z80 CTC Module should look like.
Version 1.0 of the schematic and PCB label resistors R1, R2, R3 and R4 as 100k, but it was found that if all four inputs were set to the RC2014 bus primary clock (CLK) the system would become unreliable. The value has therefore been changed to 470k to reduce loading of the clock signal.
Resistors
Fit and solder the 470K resistors R1 to R4 (shown in yellow below).
These can be fitted either way round, as they are not polarity dependent.
These should be 470k resistors, not the 100k resistors shown on v1.0 schematic and circuit board.
IC sockets
Fit and solder IC sockets for U1, U2, and X1.
Be sure to fit them with the notch matching the legend on the circuit board, so you do not end up fitting the IC the wrong way round too.
You may wish to solder the oscillator X1 directly to the board, in which case fit the oscillator now instead of the socket. The oscillator can be either the 8-pin or the 14-pin package size. The correct position for each is shown on the circuit board. Pin 1 of the oscillator is normally indicated by a ‘sharp’ corner, while the other three corners are rounded.
The sockets should be fitted in the positions shown below.
Capacitors
Fit and solder capacitors C1 to C4.
These can be fitted either way round, as they are not polarity dependent.
Resistor Network
Fit and solder the 8x10k resistor network.
This must be fitted the correct way round. The component should have pin 1 marked with a dot, as illustrated right.
Bus Connector
Fit and solder bus connector P1.
You can fit just a single row header as used by the RC2014 Standard bus, but doing so means not all the features of this module can be used. It is best to fit a double row header even if the module is initially only used with a Standard bus backplane.
To prepare the header, it should first be cut to length (if starting with a strip more than 39 pins long) and then unwanted pins must be removed. If you want to make the board as easy to insert and remove as possible, you can remove all the pins in the second row except those shown on the schematic as used and indicated below in green.
Take care to ensure the pins are parallel to the circuit board so that the board will be vertical when plugged into a backplane.
Header Pins
Fit and solder the right-angled male header pins, P2 and P3.
Take care to ensure the pins are parallel to the circuit board.
Jumper Pins
Fit and solder the jumper pins for JP1 and JP2.
JP1 and JP2 are combined as a single, 2 row by 2 pin header.
Fit and solder the jumper pins for JP3 to JP7.
Each of these is a single, 2 row by 4 pin header.
Address Select Switch
Fit and solder the 6-way DIP switch SW1.
Take care not to overheat this component when soldering.
Inspection
Remove any solder ‘splats’ with a brush, such as an old toothbrush.
Visually inspect the soldering for dry joints and shorts.
Clean the flux off with suitable cleaning materials.
Visually inspect again.
Before fitting the ICs, plug the board into an RC2014 backplane with no other boards fitted. Power the backplane and perform the following checks with a voltmeter:
- Check the supply voltage on the CTC module, between, say, U1 pin 10 and U1 pin 20. This should be 4.5 to 5.5 volts, preferably 4.75 to 5.25 volts.
- Check each input (CT0, CT1, CT2, and CT3) on connector P3 is being pulled up to at least 4.5 volts.
- Check the interrupt enable input (IEI) on connector P2 is being pulled up to at least 4.5 volts.
- Check each address switch input (Q2 to Q7) on U1 is being pulled up to at least 4.5 volts when the appropriate switch (SW1) is Off (open) and drops to less than 0.4 volts when the appropriate switch (SW1) is On (closed).
- If you have an oscilloscope or logic probe, check the clocks CLK, CLK2 and CLKX (if oscillator X1 is fitted) at jumper header JP6.
If all is well, power down and remove the CTC module.
Integrated Circuits
Insert the ICs into their sockets, taking care to insert them the correct way round, as illustrated below. Be careful not to bend any legs over.
If the oscillator has not been soldered directly to the board, insert it into the socket now. The oscillator can be either the 8-pin or the 14-pin package size. The correct position for each is shown on the circuit board. In the case of the smaller 8-pin package, it is fitted right at the top end of the socket, as indicated by the notch on the socket. Pin 1 of the oscillator is normally indicated by a ‘sharp’ corner, while the other three corners are rounded.
Test
There is no need to fit any of the jumper shunts yet.
Set the DIP switches as shown below. This sets the address to the range 0x88 to 0x8B.
WARNING: The suggested addresses clash with the official RC2014 serial / ACIA module, which does not have tight address decoding. It is assumed that most people wanting a Z80 CTC module will be using a Z80 SIO as the serial device, as the ACIA can not generate Z80 mode 2 interrupts.
Now plug the CTC module into the RC2014 backplane together with your normal working set of modules. Power up and check the system is working as usual.
Details of how to use this module can be found in the SC102 Z80 CTC User Guide.
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