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| Identify these weird EPROMs |
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| rsjsouza:
Pretty cool find. They are most probably not a simple larger EPROM but instead a custom hybrid IC - so common in those days such as the Sanyo STKs. What is unique about those is they are not fully enclosed in plastic/epoxy packaging of other common devices. |
| Benta:
--- Quote from: wraper on February 01, 2023, 08:47:10 pm ---How PAL is supposed to help with Vpp? There is no voltage compatibility. Can you give an example of 2764 with a different pinout? Half of 74LS139 or 74LS138 would do the job. --- End quote --- What's up with you, why do you carry such a chip on your shoulder? You take a longer post, pick one teeny piece out of it and blow it out of all proportion. I never said that VPP is part of the PAL circuit. The 2764 pinout in 1982 was not homogenous concerning upper address, VPP and chip selects. On top of that, no such thing as 74LS or 74HC existed in SO-packages or equivalent. It was DIP back then (or die or MIL-packaging). Period. The PAL10L8 was probably chosen for its availability in CLCC package. |
| wraper:
--- Quote from: Benta on February 01, 2023, 09:19:25 pm --- --- Quote from: wraper on February 01, 2023, 08:47:10 pm ---How PAL is supposed to help with Vpp? There is no voltage compatibility. Can you give an example of 2764 with a different pinout? Half of 74LS139 or 74LS138 would do the job. --- End quote --- What's up with you, why do you carry such a chip on your shoulder? You take a longer post, pick one teeny piece out of it and blow it out of all proportion. I never said that VPP is part of the PAL circuit. The 2764 pinout in 1982 was not homogenous concerning upper address, VPP and chip selects. On top of that, no such thing as 74LS or 74HC existed in SO-packages or equivalent. It was DIP back then (or die or MIL-packaging). Period. The PAL10L8 was probably chosen for its availability in CLCC package. --- End quote --- Look, you made a flawed argument in my opinion. Not to say argument about my post you quoted. If PAL does not fully solve pinout mismatch, there is no point using it for EPROM interchangeability. Secondly, identical 54 series existed in ceramic SMD package similar to this PAL. Look into datasheet https://www.ti.com/lit/ds/symlink/sn54ls138.pdf?ts=1675288001960&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FSN54LS138 |
| Benta:
Yeah, yeah, you're right and I have my peace. Feel better? |
| BrianHG:
--- Quote from: wraper on February 01, 2023, 09:53:29 pm --- --- Quote from: Benta on February 01, 2023, 09:19:25 pm --- --- Quote from: wraper on February 01, 2023, 08:47:10 pm ---How PAL is supposed to help with Vpp? There is no voltage compatibility. Can you give an example of 2764 with a different pinout? Half of 74LS139 or 74LS138 would do the job. --- End quote --- What's up with you, why do you carry such a chip on your shoulder? You take a longer post, pick one teeny piece out of it and blow it out of all proportion. I never said that VPP is part of the PAL circuit. The 2764 pinout in 1982 was not homogenous concerning upper address, VPP and chip selects. On top of that, no such thing as 74LS or 74HC existed in SO-packages or equivalent. It was DIP back then (or die or MIL-packaging). Period. The PAL10L8 was probably chosen for its availability in CLCC package. --- End quote --- Look, you made a flawed argument in my opinion. Not to say argument about my post you quoted. If PAL does not fully solve pinout mismatch, there is no point using it for EPROM interchangeability. Secondly, identical 54 series existed in ceramic SMD package similar to this PAL. Look into datasheet https://www.ti.com/lit/ds/symlink/sn54ls138.pdf?ts=1675288001960&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FSN54LS138 --- End quote --- You cheap slow 74LS138 added up to 41ns of propagation delay to what was already a slow 200ns eprom. How fast was the ' MMI PAL10L8-2ML ' when doing a simple 2 to 4 address decode mux? IE: only 3 of 8 product terms for each output... I bet it was a crap load faster... Also, don't forget you may be also emulating the OE and CE, not just the upper addresses as a control input element. IE: when programming 1 of 4, you will need to operate the CE while keeping all OEs disabled. When reading, the OE are preferable for address switching over using the CEs as the CEs do power-down the eprom and slow things down to awaken. This added switch in functional wiring/control makes a PAL far better suited while you would need some more additional logic ICs to wire all this up. |
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