This page will describe the standard connections to be made to your 812A4 board.

Critical Connections

There two critical connections to your 812A4 board.

The POWER Connector

Your 812A4 board is designed to run on a 5 volt power source. The board should operate within norms at voltages between about 4.9 volts and 5.8 volts. However, a regulated 5 volt power supply is the best method of providing power. The connector itself has two GND pins and 1 +5v pin. The GND pins are interconnected on the board.

This POWER connector is compatible with all of my other boards.

The BDM12 Connector

Your 812A4 board has a connector for interfacing with the Background Debug Module on the 68HC812A4. This connector uses the Motorola standard 2x3 connector. My BDM12 pod is the usual thing to connect here. You should make a note of which is pin 1. It is marked on the board. Be sure the orientation is correct when you connect a BDM pod to this port.

Optional Connections

There are several optional connectors on your 812A4 board.

SERIAL0 and SERIAL1

The 812A4 has two onboard Serial Communication Interfaces (SCI). These are TTL level 'serial' ports. Each port is brought out to a connector, namely SERIAL0 and SERIAL1. Note that SERIAL0 is also optionally wired to an onboard RS232/TTL converter, which allows you to connect directly to a PC or other RS232 compatible device. SERIAL1 is only brought out to this connector.

The pinouts for SERIAL0 and SERIAL1 are the same. These are compatible with my RS232/TTL converter cable, which is used on all of my boards and also on the BotBoard Plus.

The X1 Connector

The X1 connector is a DB9 connector designed to interface your 812A4 with a standard RS232 serial port. This connector is wired to the MAX3221 and provides the appropriate voltages for your serial port.

Only pins 2, 3, and 5 are connected on X1. All other pins are not connected.

Main Board Interconnect

The last set of connectors on the board bring all of the processor pins out to 4 2x14 headers. These are usually not installed when I build the kits since everyone seems to want a different arrangement (female vs male, top vs bottom mount, etc). J1, J2, J3, and J4 bring all 112 pins out to headers that are on a .100" grid. You can thus plug the entire board onto a breadboard or other standard drilled PCB.

Spare Connections

If you take a close look at your board, you will notice a large number of 'extra' holes that don't appear to be assigned to anything. These are a new feature I added for your use. These holes are aligned on a .100" grid, and are spare holes that you can use for whatever purpose fits your needs. Ideas include extra connections onto a breadboard, so you can wire parts into the EMPTY surface mount positions on the backside of the board. You could also add additional through hole components if needed, such as a resistor, diode, LED, or any other circuit element that might fit. There are quite a few holes available to you in different configurations.