| General > General Technical Chat |
| RE LCD Display |
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| metrologist:
I'm sorry but not sure what is wanted. The connector side is mostly direct to the P8042 chip, except one of the TEST pins, which runs through an IEC-232 xceiver chip. I can't figure out what that chip is for but the effect is that the serial data just picks up a bunch of noise. The "Control" has no connection, and output goes to TEST1 as shown in chip's block diagram below. I think the rest of the chips on the board are just serial-to-parallel data latches, but where are they getting serial input, for each of the 11 chips? I think something is defective anyway as it boots up doing different things, and at some point characters were overwriting seemingly with the clock of the serial data, then just stops and goes off. Looking at the other side of the chip there are a couple parallel busses that I guess each works a different line of the display, or maybe not. Dave mentioned that if you could not figure out the protocol of the main slave processor, then you could suck it out and work the other side. |
| PlainName:
--- Quote ---I also do not understand why MC1489 is used? --- End quote --- If it's not actual V.24 signalling it could be just to provide pin protection (+/-30V) and/or level shifting. Simpler than messing about with zeners/reistors/transistors or whateve when you don't know what some berk might try feeding into that pin. |
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