Critical Connections

There are three critical connections to the 912B32 board, and three optional connections.

The POWER Connector

Your 912B32 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.

912b32powercon.gif (5709 bytes)

There is no power switch on the board.

The VPROG Programming Power Connector

Your 912B32 board requires a REGULATED +12 volt power supply for programming the Flash memory. This +12 volt supply is only required if you are planning to program or erase the onboard Flash EEPROM. It is not required for normal operation of the board.

The 912B32 Flash EEPROM is sensitive to specific voltage levels. Therefore, you should insure that you only use a REGULATED 12 volt power supply. A non-regulated supply will damage the part as they typically have voltages in excess of 12 volts. You should check your power supply with a voltage meter to insure that the voltage is between 11.8 volts and 12.2 volts. Exceeding this range will damage the chip. This connector is labeled VPROG on the board.

912b32vprog.gif (4588 bytes)

The BDM12 connector

Your 912B32 board has a connector for interfacing with the Background Debug Module on the 68HC912. 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.

912b32bdm12.gif (3628 bytes)

Optional Connections

There are three optional connectors on the 912B32 board. Two are related to the SCI (Serial Communications Interface) port, one is related to the SPI (Serial Peripheral Interface).

SCICON

SCICON is a TTL level connection to the SCI port. You can use this connector to interconnect to another TTL level device and talk to it using standard async serial protocols. You can also connect an RS232/TTL converter, such as the BotBoard serial cable that I sell.

scicon.gif (4444 bytes)

SERIAL0

SERIAL0 is an RS-232 level connection. It requires that the onboard RS232/TTL level conversion circuit is installed. This connection allows you to connect the 912B32 board directly to a PC or other standard RS-232 device. The connector only establishes a connection using the RX, TX, and GND lines of the RS-232 standard. All other pins are not connected.

SPICON

SPICON brings out all of the pins to the Serial Peripheral Interface. SPI transmits data using a clocked I/O mechanism. It is NOT compatible with RS232 or other asynchronous communication devices.

SPICON brings out MISO, MOSI, CLK, SS, GND, and VDD to the connector. You should be aware that the SS pin is shared with the serial EEPROM on the backside of the board. If you plan to use the SS pin on SPICON for your own device, you will need to either not install the serial EEPROM chip IC3, or you will need to cut jumper JP1, and attach a jumper to CS on IC3 to another control pin on the CPU. Otherwise, the select line SS will be shared across multiple devices which will cause data errors.

spicon.gif (5492 bytes)

Main Board Interconnect

The last set of connectors on the board bring all of the processor pins out to 4 2x10 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 80 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.