Still faulty 80K

S_U_C
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Joined: Sun Feb 17, 2019 6:41 pm

Re: Still faulty 80K

Post by S_U_C »

Hi
SG <enter> turns the sound on key press ON on the MZ80K
SS <enter> turns the sound on key press OFF on the MZ80K

use B <enter> on the MZ80A to toggle the Bell function to test sound is working.
Ahmed Alqaraan
Posts: 3
Joined: Thu Nov 26, 2020 5:49 pm

Re: Still faulty 80K

Post by Ahmed Alqaraan »

I managed to transfer the RAMTEST prog using the car cassette adapter, which worked seamlessly. The code printed in the middle of the screen was ( 02032D45 ). However,  I would not know where to start interpreting this code. I gather that everything is in Hexadecimal and the last digit is the Row number of the faulty chip, but that is it!!!!

I would appreciate your interpretation. Thanks. 
hlide
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Joined: Thu Jan 25, 2018 9:31 pm

Re: Still faulty 80K

Post by hlide »

From : viewtopic.php?f=17&t=171
When an issue occurs, it displays in the middle of the display three numbers in hexadecimal: the first [byte in hexadecimal] is the pattern byte tested (bits are inverted), the second [byte in hexadecimal] is the read byte not matching the pattern byte (bits not matching are the faulty chips) and the third [16-bit word address in hexadecimal] is the faulty address to determine which row.
If you have 48KB (3 rows of 16KB):
- faulty address in ROW I ranges $1000-$4FFF,
- faulty address in ROW II ranges $5000-$8FFF,
- faulty address in ROW III ranges $9000-$CFFF.

Convert first byte and second byte into binary number. Here $02 -> 00000010b and $03 -> 00000011b so bit 0 mismatches and so the leftmost chip on the ROW I is defective. The least significant bit of a byte represents the leftmost chip and the most significant bit the rightmost chip.

When converting an hexadecimal byte into 8 bits:
D7(rightmost chip)
D6(rightmost chip but one)
D5(rightmost chip but two)
D4(rightmost chip but three)
D3(leftmost chip but three)
D2(leftmost chip but two)
D1(leftmost chip but one)
D0(leftmost chip).
MZ80KDRAM.jpg
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mz-80a
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Re: Still faulty 80K

Post by mz-80a »

Ahmed is using an MZ-80A so should be 48K. Thanks for the extra info Hlide.
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Ahmed Alqaraan
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Joined: Thu Nov 26, 2020 5:49 pm

Re: Still faulty 80K

Post by Ahmed Alqaraan »

Thank you for the explanation. I was suspecting from advice given to me by two friends, and bought few of the chips online from ebay. Once arrived I will have to look up someone, not me, to replace it.
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mz-80a
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Re: Still faulty 80K

Post by mz-80a »

I think the RAM chips are socketed rather than soldered so should be fairly easy to pull off the board and clip a new one in. If you're unconfident with hardware, like I am, then you could get a chip removal tool and a chip insertion tool (these are what I use).
MZ-80A Secrets
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http://mz-sharpworks.co.uk/
Ahmed Alqaraan
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Joined: Thu Nov 26, 2020 5:49 pm

Re: Still faulty 80K

Post by Ahmed Alqaraan »

Hi Hlide,
Thanks for the info. I did run the Basic interpreter following the RAMTEST. This time it gave me ( ERROR 6 in 64764 ). Does this correspond to the same chip ( leftmost on Row 1)?
hlide
Posts: 508
Joined: Thu Jan 25, 2018 9:31 pm

Re: Still faulty 80K

Post by hlide »

You must run the RAMTEST after each chip replacement until there is no more halt with the hexadecimal faulty pattern and address. Once running, say, a minute, without halting, it means there is no faulty chip found. Then you can try again your BASIC.
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