DarrenF
Well-known member
I understand that one may generally substitute a 2732 in place of a 2716, by doubling up the image data. This works because the Vpp pin (21) on the 2716 is generally tied high in circuit; it's the A11 line on a 2732, so as long as it has a valid status (high or low) it will provide the proper data when programmed with a double-image.
Question is, is this same concept generally applicable to the 28-pin EPROMs? For example, can I use a 27128 in place of a 2764 (double-image, of course)? Or a 27256 in place of a 27128, or 2764?
Seems like it should work, as the added address lines in the bigger ROMs replace (in order) a non-connected pin, the PGM pin, and the Vpp pin. I'm thinking those would generally be held high or low in use... but I'm here to defer my theory to your experience.
Question is, is this same concept generally applicable to the 28-pin EPROMs? For example, can I use a 27128 in place of a 2764 (double-image, of course)? Or a 27256 in place of a 27128, or 2764?
Seems like it should work, as the added address lines in the bigger ROMs replace (in order) a non-connected pin, the PGM pin, and the Vpp pin. I'm thinking those would generally be held high or low in use... but I'm here to defer my theory to your experience.
