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Update design-350-tommyprom32-pcb.md

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Typo in M27C256 description
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Tom Nisbet
2024-09-16 09:39:46 -04:00
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@@ -42,7 +42,7 @@ Note the the top picture showed the version 1.0 board and a jumper wire was need
### M27C256
The M27C256 chip needs two voltages for programming. The external power supply is providing 12.75V to _VPP Out 1_ for the the chip's _Vpp_ and _A9_ pins. The power supply is also providing 6.25V to _VPP Out 2_ for the chips _Vcc_. Note the the chip's _Vcc_ is no longer connected to the system +5V. The two _VPP Select_ switches should be in the _low_ position for normal read operation and in the _high_ position for programming.
The M27C256 chip needs two voltages for programming. The external power supply is providing 12.75V to _VPP Out 1_ for the the chip's _Vpp_ pin. The power supply is also providing 6.25V to _VPP Out 2_ for the chips _Vcc_ pin. Note the the chip's _Vcc_ is no longer connected to the system +5V. The two _VPP Select_ switches should be in the _low_ position for normal read operation and in the _high_ position for programming.
[![TommyPROM32 M27C256 programming](images/TommyPROM32-27C256-500.jpg)](images/TommyPROM32-27C256.jpg)