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PJRC Store 8051 Dev Board, $79 LCD 20x2 Display, $11 Serial Cable, $5 12 Volt Power, $8 More Components... 8051 Tools Main Page Software PAULMON Monitor Development Board Features Photos Getting Started Example Code Memory Map Ports & Pinouts Schematic & Parts Circuit Board Construction Troubleshooting Old Versions Revision List Rev 4 (2002) Rev 3 (2001) Photo Getting Started LED Blink, Asm LED Blink, C Schematic Circuit Board Construction Troubleshooting Buying Parts Rev 2 (1997) Rev 1 (1992) Code Library 89C2051 Programmer Other Resources

New Rev 4 Board

A newer version (Rev 4) of this circuit board is available. Rev 4 includes a faster CPU, more memory, more I/O and an optional LCD. We recommend you use Rev 4 for new projects. Even though this older board is no longer available, we are keeping these old pages on-line for reference to assist people who purchased or build the older version.

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Rev 4

• 22.1184 MHz (twice the speed of rev 3) - This speed allows all standard baud rates, except 300 baud. Previously 57600 was the max. Now 115200 and 38400 will work. Note: 38400 or 19200 should be used when downloading to the flash rom... 115200 usually works, but it is faster than the worst-case flash write latency.
• 32k SRAM, 24k usable for code download (rev 3 had 8k)
• 30k Flash (rev 3 had 32k, but the top 2k is now used for I/O)
• 50 I/O lines. Rev 3 had 34, and 8 were shared with the LEDs.
• LEDs have dedicated I/O, not shared with any of the 50 I/O pins
• LCD port... will have 16x2 LCD available that plugs into it for $10. This port is compatible with most character LCD that have a contoller chip like the HD44780 (industry standard for sizes up to 20x4). The board has a trim pot to adjust the LCD contrast. LCD pins are labeled on the board with names corresponding to LCD pinout of all common character displays (R/W, RS, E, Vee, etc).
• Bus expansion signals available, all signals plus 4 chip selects (256 byte range for each). Rev 3 had only part of the address bus and 1 chip select available at the I/O connector edge. Because the 50 I/O lines fill the edge of the prototype area, the bus signals are on 34 pads in the center of the new board. All the pins are nicely labeled on the board.
• Merged code/data space (previously only movc would read ram, now either movc or movx will read ram, flash, and I/O.) This change should allow Basic-52 programs to run, and at some point in the future I'm planning to make a port of Basic-52 that works nicely together with the monitor.

Development Board Items