I've got a project on my Digital Electronics course and I'm stuck. I've got five 7bit sources which I want to choose from by counter and multiplexer. But multiplexer has only one bit inputs and output and I want to have five 7bit inputs and 7 bit output. Is there any specific IC that does that thing? I read something about "group multiplexers" but I couldn't find any helpful information. Thanks in advance.
Assuming you're constrained to more-or-less standard SSI/MSI chips, you can use either:
- seven 8:1 multiplexer chips, with the select inputs driven directly from your counter
- five 8-bit tristate buffers, controlled by a 3:8 decoder chip that's driven from your counter (6 chips total)
Usually this is done by buffers, a buffer can select between two different inputs or outputs on a bus. If the enable line is asserted, it will "send the logic" through to the other side of the buffer. Otherwise the impedance is high and it has no effect on the bus.
Select a buffer based on the logic levels that your design needs, matching the voltage and currents.
Many IC's come with 8 buffers in them.