Click here for a list of the parts required to build an SC130, v1.0, Z180 Motherboard.
Experienced builders just go ahead and populate the board. There shouldn’t be any further surprises to catch you out.
Introduction
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 SC130, Z180 Motherboard should look like.
Resistors 2k2
Fit and solder the 2k2 resistors R1 to R6 (shown below in yellow).
These can be fitted either way around, as they are not polarity dependent.
Resistors 100k
Fit and solder the 100k resistors R7 to R9.
Resistor 4k7
Fit and solder the 4k7 resistor R10.
Resistors 10k
Fit and solder the 10k resistors R11 and R12.
Resistors 470R
Fit and solder the 470R resistors R13.
IC sockets
Fit and solder the IC sockets (shown below in yellow).
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 around too.
PLCC socket
Fit and solder the 68-pin PLCC socket for U4.
This type of socket can be difficult to insert into the PCB holes as there are so many fragile pins, which must be carefully aligned.
It is vital this socket is fitted the correct way around. The socket has a small chamfer on one corner, as indicated below in red.
Note the position of the chamfered corner, illustrated to the right and also below.
Quick Test
It is now worth repeating the check made earlier for a short on the power supply tracks. Connect the meter probes to each terminal of one of the capacitors, such as C1. This should be an open circuit, not a short.
Capacitor (1 nF)
Fit and solder capacitor C10.
This capacitor can be fitted either way around, as it is not polarity dependent.
The exact value of this component is not critical. The datasheet for the DS1233 specifies a value from 0.5 to 10 nF, thus a very low cost component with a wide tolerance is acceptable.
Capacitors 100 nF
Fit and solder capacitors C1 to C8.
These capacitors can be fitted either way around, as they are not polarity dependent.
The exact value of this component is not critical. The use of very cheap capacitors within the range of about 50 to 100 nF is acceptable.
Bus sockets
Fit and solder the right angled female header, 1 row x 40 pin, K2 (shown below in red).
Fit and solder straight female header, 1 row x 40 pin, K1 (shown below in yellow).
Reset button
Fit and solder push button switch SW1.
Quick Test
Again, repeat the check made earlier for a short on the power supply tracks. Connect the meter probes to IC U6 pin 14 (shown below in red) and U6 pin 7 (shown in green). This should be an open circuit, not a short. If you are using a digital meter set to measure resistance it will likely take a few seconds for the reading to stabilise as there are now capacitors on the power lines. A reading of more than 100 kΩ (100000 ohms) is acceptable.
Now measure the resistance between IC U6 pin 14 (red) and U6 pin 1 (blue). This is measuring the pull up resistor R10. It should read 4k7 Ω (4700 ohms) plus or minus 5%.
Also, measure the resistance between IC U6 pin 7 (green) and U6 pin 1 (blue). This is measuring the resistance of the reset switch (SW1). It should currently be open circuit. Again, the reading may take a few seconds to stabilise. A reading of more than 100 kΩ (100000 ohms) is acceptable. Whilst still measuring the resistance, press the reset button. The reading should now be a short circuit. A reading of less than 1 Ω is ideal, but less than 10 Ω is acceptable. The 10 ohm limit has been suggested mainly to allow for measurement accuracy with cheap meters.
Headers (straight)
Fit and solder the pin header JP1 ( 1 row of 3 pins) (shown below in red).
These may need to be cut from longer strips using wire cutters to cut the plastic.
Fit and solder the pin headers P4 and P8 (1 row of 2 pins), (shown below in yellow).
Peripheral ports
Fit and solder 1 row by 5 pin header sockets P2, P6, and P10 (shown below in yellow).
Power connectors
Fit and solder 2.1 mm barrel power socket J1 (shown below in red).
Fit and solder screw terminal J2 (shown below in yellow).
Capacitor (100 µF)
Fit and solder capacitor C9 (shown below in yellow).
It is important to fit this capacitor the right way around. The negative terminal is indicated with a ‘minus’ sign, as illustrated to the right. The negative terminal also has a shorter lead.
To make the board as low profile as possible, this capacitor can be fitted laying flat, in the position shown below.
LED
Fit and solder green LED (LED1) in the position shown below.
The LED can either be fitted vertically, with straight leads, or horizontally, by bending the leads.
It is important to fit the LED the correct way around. LEDs usually have a small flat side to indicate the cathode (the negative end). This should be positioned to match the flat side shown on the circuit board (illustrated to the right). Also, the cathode pin on the LED is usually shorter than the other pin (the Anode).
Quick Tests
Repeat the check made earlier for a short on the power supply tracks. Connect the meter probes to IC U6 pin 14 (shown below in red) and U6 pin 7 (shown in green). This should be an open circuit, not a short. If you are using a digital meter set to measure resistance it will likely take a few seconds for the reading to stabilise as there are now capacitors on the power lines. A reading of more than 100k Ω (100000 ohms) is acceptable.
Connect a 5 volt power source to J1 or J2 and perform the following tests. If you do not have a suitable 5 volt power source, connect an FTDI style serial adapter to serial port A and fit a jumper shunt to P4.
- The voltage on the two screw heads of the terminal block J2, should be between 4.75 and 5.25 volts.
- Test the status LED by touching one end of a piece of wire to U6 pin 5 and the other end to U6 pin 7.
- Check the voltage at the middle pin of U7 (RESET) is above 4.5 volts and drops to below 0.5 volts when the reset button is pressed. This should be pulled up by R10.
- Check U1 pin 31 (WR to Flash) is below 0.5 volts but rises to above 4.5 volts when a jumper shunt is fitted to the write protect position of JP1. Without the shunt fitted the signal is floating, so with a digital meter it may not be stable but should be below 0.5 volts.
- Check bus connector pin 22 (INT) is above 4.5 volts. This should be pulled up by resistor network R11.
- Check bus connector pin 36 (RX) is above 4.5 volts. This should be pulled up by R7.
Oscillator (18.432 MHz)
Fit and solder the 18.432 MHz oscillator, X1. Be sure to fit it the correct way around.
Pin 1 of the oscillator is normally indicated by a ‘sharp’ corner, while the other three corners are rounded.
Pin 1 on the circuit board is also indicated by a ‘sharp’ corner, while the other three corners are rounded.
Voltage supervisor and reset
Fit and solder the DS1233 voltage supervisor and reset device U7.
This device must be fitted the correct way around. Match the shape of the device to the legend on the circuit board.
It is necessary to spread the legs of the device to match the hole spacing on the circuit board. Do this gently so as too avoid straining the legs where they enter the plastic casing. DO not press the component hard into the board as this will also strain the legs.
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.
Quick Test
Connect a 5 volt supply or the FTDI cable (as described earlier). Check the voltage at U6 pin 1 (RESET). It should be above 4.5 volts. Check it drops below 0.5 volts when the reset button is pressed and returns to above 4.5 volts within one second of the reset button being released.
If you have a variable voltage supply you can check the voltage supervisor (U12) pulls the reset line low when the voltage drops below about 4.6 volts. This is not an exact voltage level, there is a significant tolerance, but it should trip between 4.5 and 4.75 volts.
Integrated Circuits
If all the above tests check out okay, disconnect the power and insert the integrated circuits into their sockets.
Fit the Z180 CPU into its socket as illustrated to the right. This must be fitted the correct way around. The socket and IC both have a small chamfer in the position indicated.
Take care to insert the Z180 CPU level. Avoid pressing one side in while the other side is still raised. If you need to remove the IC it is worth getting a special tool which hooks under opposite corners of component so that it can be lifted out evenly.
Fit a jumper shunt in the positions shown below.
Initial Testing
Connect the 5 volt supply and turn on. The status LED should light for a fraction of a second, then blink off for about half a second, then light again. This indicates the self test has passed.
If the self test completes correctly, power down and connect serial port A to a computer running terminal software.
An FTDI style serial adapter and cable is typically used to connect to the computer, as illustrated to the right.
The terminal software should be set for 115200 baud, 8 data bits, no parity, 1 stop bit, and no flow control. Power up and you should see the startup message.
Note: With RomWBW v2.x the baud rate is 38400 baud.
Given that the self test passed, a failure to display the start up message is most likely to be directly related to the serial port electronics or the serial adapter cable. Check for activity at the serial port connector and around the 2k2 resistors.
If all is well set the terminal software to use hardware flow control and check you still see the startup message. It is recommended that hardware flow control be used where possible.
If you have further problem the SC130 troubleshooting guide may help.
Getting Started
The SC130 User Guide can be found here.
Other information about SC130 can be found here.
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