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This page will describe the basic operation of your 912D60 board, and how the boards configuration options can be used. Basic OperationOnce you have assembled your board, you need to know how to connect power, then set it up for programming. The MC68HC912D60 part comes from the factory completely blank. Therefore, you must program it before it can do anything. To program this part, you will need a BDM12 interface pod, or an equivalent board from another manufacturer. My instructions are going to assume you are using a BDM12 interface pod. Setup for Programming and DebuggingFor the 68HC912D60Here is a list of things to do in setting up the board for programming using the 912D60 version of the chip. If you are using the 912D60A, see below.
These steps should get you setup to program your board. For the 68HC912D60AHere is a list of things to do in setting up the board for programming using the 912D60A version of the chip. If you are using the 912D60, see above
These steps should get you setup to program your board. Normal OperationFor normal operation, it is recommended that you do the following:
On powerup, the chip will enter normal single chip operation mode, and execute whatever software you have previously loaded. Optional changes to the boardI have configured this board to run just fine in stand alone mode. I have also added a few options via cut jumpers in the event that you wish to change the configuration on the board. The following describe what each of the cut jumpers on the board do. I have organized them according to functionality.
The cut jumpers are made up of three surface mount pads. To cut a jumper, you need to remove the pad that connects the outer two pads. This creates a break in the surface. You can now use the outer pads to solder on a jumper wire to connect the circuit to some other connection point.
JP6 is the only cut jumper on the component or top side of the board.
Most of the cut jumpers are in the center of the solder or bottom side of the board.
JP5 is on the bottom, in the top right corner. The following table is a summary of the cut jumpers on the 912D60 board.
A/D Conversion VoltagesThe A/D converters come by default using Vdd and Vss as the reference voltages. If you would like to connect your own reference voltages, you will need to cut jumpers. There are two sets of jumpers, one for AD0 and the other for AD1. To replace the Vrh and Vrl for AD0, cut JP1 and/or JP2 on the bottom of the board. JP1 is connected to the Vrh pin and to Vdd. If you cut JP1, you can replace Vrh with your own signal by either soldering a jumper to the appropriate pad on JP1, or connecting to pin 67 of the CPU. Likewise, JP2 is connected to pin 68 which is Vrl. To replace the Vrh and Vrl for AD1, cut JP3 and/or JP4 on the bottom of the board. JP3 is connected to the Vrh pin and to Vdd. If you cut JP3, you can replace Vrh with your own signal by either soldering a jumper to the appropriate pad on JP3, or connecting to pin 86 of the CPU. Likewise, JP4 is connected to pin 87 which is Vrl. RS232/TTL ConversionOne of the larger optional sections is the RS232/TTL conversion section. This section uses a MAX3221CAE part, which is a low power converter. The nice thing about this converter is it uses extremely little power in its shutdown state (approximately 5 uA). Thus, if you wish, you can install the part and practically ignore it. Otherwise, you can leave off IC2, C5, C6, C7, and C8 and the board will function without it.
The MAX3221 part will stay in shutdown until it finds a valid signal on the RX line of the SERIAL0 connector. When this happens, the part will resume operation by starting the charge pump. If you wish, there is an additional connection that isn't implemented on this part called the INVALID/ pin. I have brought this connection out to an unmarked pad on the bottom side of the board. It is called the INVALID pad, and can be seen in the above diagram. Serial EEPROMThe Serial EEPROM used on the 912D60 board is a Microchip 25LC640, which is an 8k x 8 serial EEPROM that is SPI compatible. I have wired this part directly to the SPI port on the board, and it uses the SS pin of the SPI port as the chip select. If you wish, you can omit the serial EEPROM if you don't plan to use it. If you do install the EEPROM, there are several cut jumpers that you can use to change the configuration. The default wiring works great when this device is the only thing on the SPI bus. The default wiring has the IC4's chip select connected to the SS pin on the SPI port. To change this, you will need to cut jumper JP1, and rewire a different chip select via an I/O output pin. Two other pins are connected to defaults through cut jumpers. JP8 defaults the HOLD\ pin to high, and JP9 disables the write protect mechanism. You need to understand how the serial EEPROM works before changing these defaults. Empty SMT layoutsI also included a few empty SMT layouts in some spare room I found on the backside of the board. These parts are labeled EMPTY1-5, and are available for your use.
Empty HolesLooking at the topside of the board, you will notice all of the through hole parts have outlines around their holes. You may also notice a large number of holes that are 'extra'. These are put on for your use. For example, if you need to add a pullup or pulldown resistor, or perhaps add an additional connector to interface with the EMPTY SMT layouts, you are free to use these extra holes. They are aligned on a .100" grid, and can be stuffed with any part you see fit.
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