This page describes the assembly process for the 812A4 board.

The 812A4 board makes use of several surface mount parts. If you would like to see a tutorial on soldering surface mount parts, you can check out instructions on Soldering Surface Mount Parts.

Parts List

The following parts make up optional components. These circuits may be left off if you don't intend to use them.

Your finished board will look something like this:

1. The first part to mount is the CPU (IC1). Be sure to note where pin 1 is. The 68HC812A4 has a small indent in one corner that indicates pin 1. The indent is distinctly smaller than the other corner dots. The board has a small 1 near pin 1. It can be seen in the picture below.
   
2. Solder IC1 onto the board. (See Soldering Surface Mount Parts for instructions).
3. Now mount two surface mount capacitors (C5 and C9) on the top side of the board. These are bypass capacitors, and should be installed.
4. Turn the board over and solder on capacitor C8. This is also a bypass capacitor, and should be installed.
5. Time to mount the optional RS232/TTL level conversion. Because of spacing considerations, I suggest mounting the parts in the following order: IC3, C1 and C2. On the topside of the board, mount C4, C3.
6. Mount IC3, which is the optional serial EEPROM.
7. That's it for the surface mount parts! Now, install the 2 22pF caps C6 and C7. These parts are marked with a 220 on the case. You can elect to either solder each part, or you can install most of the through hole parts and solder them all at the end. If you want to install all parts first, you should consider bending the wire leads on the backside after they are inserted to hold them in place.
8. Install R1, which is a 10M 1/8 watt resistor. Note: Anything between 1meg and 10 meg will work just fine. Some kits come with 1 meg, some with 10 meg. It doesn't matter.
9. Install the crystal Q1, which is up to a 16mhz crystal.
10. Install RN1, which is a 10k resistor network in an ISOLATED configuration. That means the one package contains 4 individual resistors. Note that pin 1 is usually marked with a dot on the resistor. Pin 1 on the PCB is also marked.
11. Install IC2, which is the MC34064P-5 Low Voltage Reset component. This will reset the CPU if the voltage drops below about 4.5 volts. You should align it so the case outline matches the silkscreen.
12. Install SW-RESET, which is a 6mm reset switch.
13. Install C10, which is a 10uF capacitor. Note that this part is polarized, meaning you need to insure that the '-' terminal of the cap is installed in the '-' pad on the board. The board has only the '+' pad marked. The other hole is the '-' pad.
14. This is a great time to flip the board over and solder the parts, if you haven't done so individually.
15. The POWER connector is a 3 pin Molex KK connector. Install it.
16. If you wish, you can install SERIAL0 and SERIAL1, which are 4 pin connectors. This are optional TTL level access points to the SCI ports.
17. Install the BDM12 connector, which is a 2x3 header. Solder these parts in place.
18. The last thing to install is X1, which is an RS232 level connector for SCI0 (SERIAL0). You should install this if you have installed the RS232/TTL level conversion circuit from step 5. This part is mounted by inserting the PCB between the solder cups, as seen in the overview picture above.