I'm super new to electronics and am wondering if there is anything that behaves like the reverse of a shift register... as in parallel in and serial out instead of serial in and parallel out. I know there are multiplexers, but they don't seem to operate in the same way as a shift register (with latch and clock signals), thanks.
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2\$\begingroup\$ Do a Google search for "parallel to serial shift register". I use the CD4021 but there are others. \$\endgroup\$– Dwayne ReidCommented Apr 4, 2015 at 18:48
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1\$\begingroup\$ The Parallel In - Serial out can do this for you. \$\endgroup\$– nidhinCommented Apr 4, 2015 at 18:49
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\$\begingroup\$ The circuit is called a 'Parallel-Load Shift Register'. \$\endgroup\$– Tom CarpenterCommented Apr 4, 2015 at 21:00
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\$\begingroup\$ One of you should provide a response so I can mark it as the correct answer... helped a lot with finding a good part \$\endgroup\$– Jacob EdwardCommented Apr 15, 2015 at 0:23
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2 Answers
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A parallel-in, serial-out shift register (PISO) can read several parallel inputs (usually 8) and serially output the data. Much like a SIPO shift register, a PISO has an internal storage register that always contains the states of the parallel inputs. When the "load" pin is pulsed, the contents of the storage register are transferred into the internal shift register. Then when the "clock" pin is pulsed, the data bits in the shift register are shifted one bit over toward the serial output. PISO shift registers can also be cascaded by connecting the serial input of one register to the previous register's serial output.
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Like halailah mentioned, you are looking for a PISO, a typical parallel-in, serial-out shift register. One with the specs you are searching for is the SN74HC165; these are used often, and many hobby stores have them. probably.
You can also use a normal SIPO shift register like the 74HC595 and then connect general transistors, or even better FETs/MOSFETs to the outputs (if you use general transistors, then do not forget to add a resistor in between).
You can use that to enable one or a few outputs at a time and link them all together to one read pin on your microprocessor or such. Doing it that way also allows you to read analog voltages, where I am not sure if the SN74HC165 can also read analog voltages by default (you can read the datasheet if you need analog voltages).
