TESLA PROM Programmer Board

 

Under Construction ! (so content not necessarily correct)

 

I am working on the design for a TESLA PROM Programmer, it will be similar to the original Acorn PROM Programmer but will only be able to program 16-pin TESLA PROM's.  I am also rewriting PROMER2 (PROMER3) to work with either or both programmers.

Reading PROMs

Tesla PROMs are read in exactly the same way as the NSC devices, the address and data lines are on the same pins and the enable pin is taken low.

Programming

The following summarises the programming procedure as detailed in the manufacturers data sheets for the NSC 74S571, Tesla MH74S571 and Texas Instruments

You can see that programming the NSC PROMs is significantly different hence the need for a new programming for the Tesla devices.  The procedure for programming the Texas Instruments PROMs is interesting because it is almost identical to the Tesla procedure.

Both NSC and Tesla PROMs output '0's when unprogrammed.

NSC PROM Programming Procedure

  1. apply 5V Vcc, Enable pin high and write the address

  2. increase Vcc to 10.5V

  3. raise the voltage on the pin to be programmed ( to '1') to 10.5V

  4. pulse Enable low for 10uS

  5. remove the programming voltage and reduce Vcc (to 4V) for verification

  6. repeat 2. to 5. up to 10 times or until the bit is verified as programmed

  7. repeat 2. to 5. an additional 5 times

Note this whole process is for a single bit

The supply voltage should only be held at 10.5V for a maximum 25% of the time to avoid overheating.

 

Tesla PROM Programming Procedure

  1. apply 5V Vcc, Enable pin low and write the address

  2. the location can then be read to confirm that the bit needs to be programmed (to '1')

  3. take the Enable pin high and pull the bit to be programmed down to 0V

  4. increase Vcc to 10.5V

  5. (after between 10uS and 1mS) pulse Enable pin low for 1mS

  6. (after between 10uS and 1mS) reduce Vcc to 5V and remove pull down on programmed bit

  7. (after a minimum of 10uS) the bit can be verified by taking Enable low, Vcc should then be switched off to reduce power dissipation

  8. the process is repeated up to 8 times until the bit is verified as programmed, after a second pulse the pulse length is increased to 20mS (for the remaining 6 pulses)

Note this whole process is again for a single bit

The device should be allowed to cool with Vcc off for 3 to 4 times the programming pulse width between bit programming.

 

Texas Instruments PROM Programming Procedure

  1. apply 5V Vcc, Enable pin low and write the address

  2. the location can then be read to confirm that the bit needs to be programmed (to '1')

  3. take the Enable pin high and pull the bit to be programmed down to 0V

  4. increase Vcc to 10.5V

  5. (after between 10uS and 1mS) pulse Enable pin low for 1mS

  6. (after between 10uS and 1mS) reduce Vcc to 5V and remove pull down on programmed bit

  7. (after a minimum of 10uS) the bit can be verified by taking Enable low, Vcc should then be switched off to reduce power dissipation

  8. the process is repeated up to 8 times until the bit is verified as programmed, after a second pulse the pulse length is increased to 20mS (for the remaining 6 pulses)

Note this whole process is again for a single bit

The device should be allowed to cool with Vcc off for 3 to 4 times the programming pulse width between bit programming.

 

 

The Tesla data sheet doesn't specify how many times to repeat the programming sequence however its is identical to the programming sequence for the Texas Instruments 54/74188A and 54S/74S series PROMs and so I have taken that information from the TI data sheet.

The two processes are quite different, NSC fuses are blown by applying 10.5V to the bit whilst Tesla fuses by pulling the bit low, both whilst Vcc is raised to 10.5V.  This requires significantly different hardware hence the easy option is to design a 2nd board for Tesla PROMs.

 

 

I have carried out some tests with different programming pulse lengths and found that generally a bit will successfully program in 1 to 3 x 1mS pulses however sometimes they can take longer up to 15 x 1mS pulses.  The Texas Instruments data sheet states that 'programming is guaranteed if the pulse applied is 10mS long'

 

My code applies up to 10 x 1mS pulses checking for success after each pulse and if that fails then a final 10mS pulse is applied, this helps to keep the overall programming time short.

 

 

Measurements

 

I've taken some current measurements during reading and programming:

 

 

 

 

Schematic

Bill Of Materials

 

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