Burkhard Kainka
About the article

89S8252 Flash Microcontroller Board

Educational hardware and softwareplatform for the Microcontroller Basics course

89S8252 Flash Microcontroller Board
A microcontroller board that serves as the foundation for a programming course must be easy to use while still having all the ingredients of a modern microcontroller with its peripherals. This makes such a board interesting for old microcontroller hands as well!Anyone who wants to convert his own ideas into circuitry will usually achieve the desired result more quickly with a microcontroller than with ‘conventional’ electronics. However, in many cases the programming is relatively laborious. Consequently, Elektor Electronics have developed the new Flash Board. The flash program memory and a wellconsidered system design ensure easy and fast programming.Our criteria for a new microcontroller board were based on the following objectives: the circuit to be developed should meet the needs of beginners as well as experienced users; the system should be designed from the start to handle various programming languages, including assembler, BASIC and C; and furthermore, the system should be easily extendible and easy to program. In addition, a program that has been transferred to the board should be retained when power is switched off, in order to avoid the tedious process of (re)programming EPROMs. This means that the board should also serve as a device programmer.
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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.

Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

Extra info / Update
A few users running Windows XP Home Edition SP2 have reported problems. Apparently, unaccounted for CTS line activity occurs on the RS232 port when P1 is programmed to supply fast pulses. This causes XP to hang even if the relevant COM port is not accessed.
Also, a timing problem was discovered in the original download utilities. Both problems have been addressed and an update is available at: www.b-kainka.de/basismufaq.htm
Component list
R1,R2,R6,R7 = 27kOhm
R3,R5 = 1kOhm
R4 = 47kOhm
P1 = 10kOhm preset H
C1,C2 = 22pF
C3,C5,C6,C14,C15 = 100nF ceramic
C4,C7-C11 = 10µ F 63V radial
C12 = 1000µ F 16V radial
C13 = 100µ F 10V radial
D1,D2 = zener diode 4V7, 500 mW
D3 = BAT85
D4 = 1N4001
IC1 = AT89S8252 24PC
IC2 = HC126
IC3 = 74HCT573
IC4 = 62256 120 ns
IC5 = 74HCT00
IC6 = MAX232
IC7 = 7805
K1,K2 = 9-way Sub-D socket (female), angled pins, PCB mount
K3 = 14-way boxheader
K4-K7 = 8-way SIL pinheader
K8 = 34-way boxheader
K9 = socket for mains adaptor
S1 = pushbutton, make contact
X1 = 11.0592 MHz quartz crystal
PCB, order code 010208-1
Disk, project software, order code 010208-11
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