Category Archives: MCS-51 family

This is simple development board for Atmel AT89 series of microcontrollers that uses ISP programmability I found in sixca.com. This is good start for learning with MCS-51 base projects.

This board supports Atmel microcontroller series like AT89S51, AT89S52, AT89S53, AT89S8252 with DIP40 pin packages. The board uses ISP programming method through parallel port adapter. It has all I/O connectors, single sided PCB. It has on board voltage regulator 7805.

AT89_Schematic

Programming of this microcontroller never been so easy. Just use simple download cable:

For programming use ISP-3v0 software included in packed project archive.

To program chip:

1. Connect ATMEL ISP cable to PC parallel port and power supply.
2. Run ISP3.0 for Windows95/98/ME use ISP-3v0.exe and WindowsXP/2000/NT use ISP-XP.bat .
3. Select your devices from drop down list menu.
4. Click “Open file” to open hex file.
5. Click “Write” to program device.

Board in use

Download example code to blink led on port2 (Compile with KEIL C51).

Project files and ISP-3v0 are in this package: Project files

Microcontrollers family AT89C has parallel programming interface of flash memory. In order to write information we need to supply programming voltage +12V and for controlling almost all pins of ports are used. This is why parallel programming is done in special devices – programmers.

Microcontrollers AT89S besides parallel programming ability have ISP programming ability. Using Serial programming interface doesn’t need +12V of programming voltage, because inside interface is voltage converter included.

When programming AT89S microcontroller using ISP method there are only four lines needed – RESET, SCK, MOSI, MISO. Using ISP programming method it is not necessary to remove microcontroller from circuit ISP is so called in-system programmability. How does it look in circuit shows following illustration:

Programmer connects to microcontroller using ISP header. Resistors R1-R4 are used to avoid conflicts of signals between programmer and peripheral circuitry.

ISP programmer can be connected to LPT port which controls all programming process and synchronizes overall process. Programmer is same as AVR ISP programmer and AT89S microcontrollers can be programmed using popular software like PonyProg.

Microcontrollers with MCS-51 architecture of Atmel are one of the first product with inbuilt Flash program memory. Such attitude of Atmel gained popularity of its products among embedded system designers and hobbyists. Built in flash memory reduced the overall cost of microcontrollers. As we know the main popularity of Atmel is gained by AVR microcontrollers where flash memory is used with self programming abilities. This step of Atmel organisation made other companies like Motorola, Philips, Texas Instruments to release flash microcontrollers.

All Atmel microcontrollers of family MCS-51 with flash memory are marked as “89”. This rule is followed by other manufacturers like Philips, Temic, SST, ISSI, just Winbond corporation marks them as W77 and W78.

Write cycles of AT89 family microcontroller flash are over 1000.

Reading AT89 microcontroller markings can give yo ua bunch of information like letter “C” (AT89C) says that chip is based on CMOS technology and parameters are similar to similar microcontrollers of other organisations like Intel 80C51 or Philips 87C52.

Marking AT89LV means that power supply level is reduced to 2.7V.

AT89S has ability to be in system programmed (ISP) using ISP interface.

AT89LS has ISP ability but also should be powered by voltage of 2.7V.

There are two types of cores of MCS-51 family:

• C51 – standard core with 128 bytes of RAM and 3 timers;

• C52 – modified core with 256 bytes of RAM and 3 timers.

Marking of C55 or C54 or C58 indicates the amount of program memory (flash) from 16 to 32 kbytes.