Unused 8051 pin gets assignment

In an 8051-based system without external program memory, the program-store enable (PSEN) pin is useless. However, you can indirectly control this pin using software. To do so, you execute the move-constant- (MOVC-) instruction-implementing table look-up. By accessing locations in external program memory (which is actually nonexistent), you can produce pulses on the PSEN line without disturbing program flow. Although you need a register for storing output data, you don’t have to install a decoder.
source:http://edn.com/archives/1996/010496/01di7.htm

A serial to parallel converter using the AT89C2051

The example program included with the PG2051 evaluation kit is a basic serial to parallel converter written in 8051 assembler. This is probably a good example of the uses to which an AT89C2051 can be put - it would be hard to get a serial to parallel converter much simpler than the single 20 pin IC in this circuit. The program is meant to serve as a useful example of 8051 serial routines and other programming, whether or not you actually need a serial to parallel converter.
Source: http://airborn.com.au/serial/sertopar.html

Accelerometer Schematic

Below is a rough schematic of the layout of the accelerometer PC board looking from the component side. The microcontroller is an Atmel AT89S8252, an 8051 clone. This microcontroller is in-circuit programmable using an SPI interface. The SPI pins are also used to drive the MMC. To permit the dual use there is a jumper block (located below the 74AHC244, marked "P" and "R") that allows the pins to be connected for programming (P) or running the code (R).
Source:http://www.randomuseless.info/accelerometer/schematic/schematic.html

Combine two 8-bit outputs to make one 16-bit DAC

Inexpensive, 16-bit, monolithic DACs can serve almost all applications. However, some applications require unconventional approaches. This Design Idea design concerns circuitry I recently designed for a tunable-diode laser spectrometer for a Mars-exploration application. The control circuitry included two 16-bit DACs that interface to the radiation-hardened, 8051-variant 69RH051A microcontroller.
Source:http://www.edn.com/article/CA454640.html

MIDI Drum Machine Project

The MIDI Drum Machine began in the Fall of 1991 as a project for a microprocessor system design course, shortly after I wrote PAULMON1, the 8051 monitor/debugger. A friend, Rod Seely, both a musician and electronics hobbiest suggested I design something using the Musical Instrument Device Interface, MIDI, that would be COOL and would work together with his collection of MIDI keyboards and synthesizers. Of course, I wanted to build something that could end up as a finished commercial product.
Source :http://www.pjrc.com/tech/midi-drums/drum-intro.html