SRG8
IEC shift register (SRGm)
IEC register marked SRGm with m stages; the clock carries the shift arrow and moves data one place each cycle.
IEC
IEC · SRG4
IEC bidirectional (universal) shift register
IEC shift register with mode inputs that select shift right, shift left, parallel load or hold.
In plain English
What does IEC bidirectional (universal) shift register mean?
A universal shift register is drawn as an SRG element with two mode-select inputs grouped to produce modes 0 to 3. The clock label shows shift right under one mode and shift left under another, while data inputs are labelled with their mode and control numbers, such as 1,4D for serial right input and 3,4D for parallel load.
A simple example
These devices are used in data conversion, sequence generation and bidirectional serial links. Reading the compound labels left to right, mode first then clock, tells you exactly when each input is used.
What the drawings help you do
The symbol does not state which mode is safe to change during clocking. Mode changes are normally made with the clock inactive.
This particular reference
IEC shift register with mode inputs that select shift right, shift left, parallel load or hold. A single-direction SRG register has no mode inputs and shifts only one way.
- Signal
- Electrical information passed between devices, rather than necessarily the main power supply.
- Schematic
- A drawing showing function and connections rather than physical appearance.
Read the source: Overview of IEEE Standard 91-1984: explanation of logic symbols (SDYZ001A)
IEC · SRGm element with mode inputs selecting shift right, shift left and parallel load
Qualifying-symbol and dependency conventions as explained in TI's public overview of IEEE Std 91-1984, which incorporates IEC 617-12 work. Independent educational drawing; not certified IEC geometry or an IEC database identifier.
Shown as an independently authored educational illustration. Use the cited publication and drawing legend to verify the required drafting form.
Schematic · SRG4
What it represents
A universal shift register is drawn as an SRG element with two mode-select inputs grouped to produce modes 0 to 3. The clock label shows shift right under one mode and shift left under another, while data inputs are labelled with their mode and control numbers, such as 1,4D for serial right input and 3,4D for parallel load.
These devices are used in data conversion, sequence generation and bidirectional serial links. Reading the compound labels left to right, mode first then clock, tells you exactly when each input is used.
The symbol does not state which mode is safe to change during clocking. Mode changes are normally made with the clock inactive.
How to read it
- Decode the mode inputs first.
- Compound labels such as 1,4D give mode then clock.
Information to show or reference
- Show the mode-select grouping.
- Label both shift directions on the clock.
- Label serial and parallel data inputs with their mode numbers.
A distinction that matters
A single-direction SRG register has no mode inputs and shifts only one way.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
Overview of IEEE Standard 91-1984: explanation of logic symbols (SDYZ001A)
Shift right and left labels and M dependency examples.
About this graphic
This illustration was authored independently by Elora Grid to explain the concept. It is not reproduced from a customer drawing, an official standard graphic or a manufacturer CAD file. Its correspondence to an exact IEC or IEEE symbol identifier has not been certified.
SVG and DXF downloads contain this original artwork. DXF uses unscaled drawing units; a GA envelope supplies no product dimensions, clearances or fabrication information. Original artwork is available under CC BY 4.0. Third-party references retain their own terms.
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