Simplemodification the Easy programmer's hardware and firmware for 89C55WD.

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I got many mail asking for modificationthe Easy-Downloader V2.0 for the 89C55WD. They told me that ATMEL stopproduction the 89C55. They make 89C55WD instead. Also a friend from Brazilsent me two 89C55WD. I think better modify the easy V2.0 for such chip.After reading ATMEL datasheet, I checked different between 89C55 and 89C55WD.Here is what I get.
 

Items	89C55	89C55WD
1. address line A14	P3.0	P3.4
2. status line RDY/BSY	P3.4	P3.0
3. mode select lines	P2.6, P2.7, P3.6, P3.7	P2.6,P2.7,P3.3,P3.6,P3.7
4. minimum program pulse width	1us	200ns
5. minimum erase pulse width	10ms	200ns
6. Vdd during erasing	+5V	+6.5V
7. Vpp	+12.5V	+12.5V

Let get back study the Easy V2.0 schematicagain.

Since the 89C51 and 89C52 do notuse A14, thus for 89C55WD we can tie A14 that comes from P2.6 to pin 14.The 89C55WD uses pin 10 for RDY/BSY.  The mode selection needs moresignal, i.e. P3.3 so I thought may be I can use P3.2 that used to be RDY/BSYfor such signal, however doing this I will not have the status line tomonitor while programming. May be I can try with software delay instead.

Here is the new schematic for Easy V2.1.Click at the image to get the complete schematic. We see that the modificationis very simple, just cut pin 14 of ZIF and tie A14 signal to P3.4. I usedP3.2 of master chip for mode selection P3.3 pin13 of ZIF, that's all. Everythingremain the same as V2.0.

Figure 3 shows BOM or Bill ofMaterials for V2.1. Please note that the signal for serial port connectedto DB9 connector requires the CABLE to be cross over between TxD and RxD.Such cable commonly know as null modem cable. U2 or master chip can bewhatever chip having pins and software compatible to MCS51, say 89C51,89C52, or 89S8252. R4 and R5 may not find easily, you may make it withtwo resistors series connected, say for R4 by using 2k + 150 Ohms.
 

Easy-Downloader V2.1 89C51/89C52/89C55WD Revised: Sunday, August 18, 2002          Revision: 1 Bill Of Materials        August 18,2002      11:52:03 Page1 Item Quantity Reference Part

1         2          C1,C2              30pF disc ceramic cap 2         6          C3,C7,C8,C10,C11,C12         10uF 10Vdc electrolytic cap 3        1           C4                   0.1uF disc ceramic, or mutilayer 4        1           C5                   1uF 16V electrolytic cap 5        1           C6                   100uF 25V electrolytic cap 6        1           C9                   10uF 10V electrolytic cap 7        1           D1                   1N4001 silicon rectifying diode 8        1           D2                    LED  small dot LED 9        1           J1                     DC input  10      1          Q1                    2N2222 NPN transistor 11      1          R1                   10KX8  R pack 12      1          R2                   1k 13      1          R3                   250 Ohms 14      1          R4                   2150 Ohms 15      1          R5                  1150 Ohms 16      1          R6                   8.2k 17      1          R7                  10k 18      1          U1                   LM7805C/TO220 +5V Voltage regulator 19      1          U2                   AT89C51 4-k FLASH Microcontroller 20      1          U3                  40-pin Zero-Insertion-Force SOCKET 21      1          U4                  LM317/TO Adjustable linear regulator 22      1          U5                  MAX232A RS232 Level converter 23      1        VB1                 SUB-D 9,  for NULL MODEM CABLE 24      1          Y1                  11.0592MHz Crystal

Figure 3: Billof Materials

Making the programmer board is easy withsimple universal PCB or even on the breadboard. But the latter is justfor testing not suitable for practical usage.

Before putting the chip into the board.Here is hardware check list.

1. Check the DC output from AC adapter,it should provide approx. +15V or higher.

2. Check the polarity of the DC jack, thecenter must be positive. I add D1 to protect wrong polarity.

3. Check Vcc-GND for U2, U3 and U5. Itmust be +5V.

4. Now check Vpp, measure at pin 31 ofZIF socket, it should be approx. +12.5V. Let tie P3.3 of master chip to+5V, the Vpp will then be approx. +5V. The value of R3, R4 and R5 are designedfor such output.

5. Let ask someone to help program theEZ55.hex into the master chip, say 89C51.

6. Turn off the board power and put everychip to the PCB.

Before try with EZ4 we can check the EZ55firmware and our board wiring by firmware check list below.

1. Run Hyperterminal with 9600 8n1 no flowcontrol.

2. Connect the programmer board to COM1,say.

3. Before power up the programmer board,put a target chip to ZIF socket. Then turn on power.

4. Press ENTER key on PC, you must get,
 

Easy-Downloader V2.1 for ATMEL 89C51/52/55WD >

5. Try with command 'g'
 

ok  >g  found 89C55-12V  nonblank 8659 bytes  bytes counter 3484  ok  >

6. Now try with EZ4.
 

Here's the beta version of firmware formaster chip, EZ55.HEX and the source codefile EZ55.C.

The source code was compiled with DunfieldMicro-C for 8051 release 3.2.

Note:

1. During erase the chip,ATMEL recommends to raise Vcc from +5V to +6.5V. I tested with +5V as 89C55,it works fine. However, if need such +6.5V, I'm thinking to raise the GNDpin of 7805 with two silicon diodes (0.6X2), this would make the outputof 7805 to approx., +6.2V. But the master chip doesn't have enough i/oto control it. So we may try supply both chips with +6.2V without the enableline! So far I haven't tested it yet.

2. EZ55 runs well under newPC software,EZ4

3. The signature byte of89C55WD is located at 0x100. When the EZ4 connects the board, it will showfound 89C55, the same as 89C55 put of ZIF. However A14 is now not tie toP3.0, instead to P3.4. So if you still have the 89C55, and need the programmerto program it, you may make a jumper to select between P3.0 and P3.4 forA14 signaling.

4. It is a good practiceto put the target chip in/out while the programmer's board power turnsoff. And carefully put the right position, otherwise the target and masterchips may dead.