The MMC prototype using a PIC16F876 running on 3.3v. The MMC is in a socket which is soldered to a small pcb.
Parts used:
16F876 28 pin mcu
Max233A for serial
An 24C65 I2C eeprom
LM2937 3.3 reg.
10 Mhz xtal
Molex MMC socket
DB9 connector
Melabs? Proto3 board
Misc: 4 caps, 6 res, pwr LED,reset switch and headers?
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The small pcb has a 7 pin male header at the bottom which plugs into a female header on the prototype. This allows one to use the? alternative connection shown below if an MMC socket is not available. The DB9 serial connector serves a dual purpose. It is used for data I/O to and also to program the 16F876 serially. A MAX233A was used instead of a MAX232 simply because it requires no external capacitors. In order for the 16F876 to operate at 3.3v its built-in brownout protection feature (BOR) has to be disabled. The I2C eeprom is used as a temporary storage area. The MMC writes data in blocks of 512 bytes, therefore it is not possible to write just one or two bytes at a time (does not apply to reading). Therefore one needs to store the data somewhere until it reaches a minimum of 512 bytes. Any I2C eeprom can be used as long as it can hold 512 bytes or more of data.
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