kjennejohn
New Member
Mike said:Could you list the IC number and IC type? I can't make out the IC type from the picture.
IC1 -
IC2 -
IC3 -
etc...
Hi. It's all been done and is sitting on this page spread over a few posts, just before your excellent drawing. You'll find the chips by IC number, their type, and jumps to data sheets for all these.
Nice job, Hackable. Unfortunately, something isn't right. You say two pins on the connector go to pins 5 and 11 of IC2. These are data output pins. Those should be going to the inputs of the HC154 and the HC138. I'll explain:
The 4094, like the 5821, takes serial data in on every clock. After you've shifted in 8 bits (more in our case, since we have more than one chip), you bang the STROBE line to latch these bits into the output register. You can just pull the OE (Output Enable) line true and forget it. The old data disappears immediately to be replaced by the new data. This is true for all these serial-to-parallel chips, the 5821s and 4094s. The chip designers realized the user may want to put out a long stream of data, so they provide a pin that allows serial data to 'overflow' to the data input of the next chip in line. You pump 64 bits to fill the 5821s and 8 more to fill the 4094 (and maybe 8 more to fill the other 4094, for reasons unknown). I think some more checking will show that pins 9 or 10 (Q's and Qs, the 'overflows') of the 4094 connect to pin 2 of the first 5821 in the chain (IC6?).
Your check of the connector pins show pins 15 (OUT ENABLE) and 3 (CLOCK) of IC2 are what we'd expect. I think you need to check and see if pins 1 (STROBE) and 2 (DATA) are really hooked to the connector pins somewhere, not pins 5 and 11, which are data outputs. I believe you'll find that 7 of the 8 data outputs of the 4094 (pins 4, 5, 6, 7, 11, 12, 13 and 14) go to the seven input pins of the HC154 and HC138. Which of the 4094s this is you'll have to find out yourself.
As for performance: this means the processor has to pump 72 (or 80?) bits for every row to be displayed. And it has to do THAT 21 times to fill the display. This is a VERY busy processor, but it only has one job, and these chips can be clocked up to 5 MHz. So, while outputting the previous row, you clock the next row's worth of data in, then pump the STROBE. You'll want to update the display, say, 18 times a second. That means you'll have to refresh the data in the latches 21x18 times a second, or 378 time a second, which is a row every 2.6 millisecond. A row-display is 72 bits, for a serial data rate of 2.67mS/72, or one bit for every 3.67 uS. No problem. Piece of cake. A mere 27K-bits per second. Not even modem speed.
Enough already. Later!
kenjj