Tiny Tapeout > Tiny Tapeout Chips > Tiny Tapeout SKY 26a > 928 Universal Shift Register (SN74LS194A compatible)
928 Universal Shift Register (SN74LS194A compatible)
928 : Universal Shift Register (SN74LS194A compatible)
- Author: nicholas
- Description: 4-bit bidirectional universal shift register: hold, shift right, shift left, parallel load, async active-low clear.
- GitHub repository
- Open in 3D viewer
- Clock: 1000000 Hz
How it works
This design implements the behaviour of a TI SN74LS194A-style 4-bit bidirectional universal shift register.
- Clocked on rising edge of
clk - Asynchronous active-low clear using TinyTapeout
rst_n - Mode select via
S1,S0:00: Hold (no change)01: Shift right:QA<-SR,QB<-QA,QC<-QB,QD<-QC10: Shift left:QD<-SL,QC<-QD,QB<-QC,QA<-QB11: Parallel load:QA..QD <- A..D
How to test
- Drive
rst_n = 0briefly to clear all outputs to 0, then setrst_n = 1. - Set
S1,S0:- Hold:
00 - Shift right:
01(provide data onSR_SER) - Shift left:
10(provide data onSL_SER) - Parallel load:
11(setA..Dthen clock once)
- Hold:
- Toggle
clkand observe outputsQA..QD.
External hardware
None required. (Optionally: switches for inputs and LEDs for outputs on a TinyTapeout demo board.)
IO
| # | Input | Output | Bidirectional |
|---|---|---|---|
| 0 | S0 (mode select) | QA | |
| 1 | S1 (mode select) | QB | |
| 2 | SR (serial in for shift-right; enters QA) | QC | |
| 3 | SL (serial in for shift-left; enters QD) | QD | |
| 4 | A (parallel in) | ||
| 5 | B (parallel in) | ||
| 6 | C (parallel in) | ||
| 7 | D (parallel in) |