CTR-SYNC
Synchronous binary counter
Updates its binary count from a common clock with the documented count-enable, load and clear controls.
Schematic
IEC · CTR4
IEC synchronous binary counter (CTRm)
IEC counter marked CTRm, where m is the bit count and the cycle length is 2 to the power m.
In plain English
What does IEC synchronous binary counter (CTRm) mean?
The general additional drawing mark CTRm identifies a counter with m bits and a cycle length of 2 to the power m. In IEC form the clock appears as C with a + to show counting up, and load, clear and enable inputs use dependency notation such as M1 for load mode and G for count enable. Outputs carry binary weights 1, 2, 4 and 8.
A simple example
A reader should identify the synchronous and asynchronous inputs from their prefixes, then find the carry output, often labelled CT=15, used to cascade stages. On control drawings counters represent event totals, batch counts or divide-by-n timing.
What the drawings help you do
The symbol does not state maximum count rate or whether the clear is synchronous, except through dependency labels. Read the prefixes carefully.
This particular reference
IEC counter marked CTRm, where m is the bit count and the cycle length is 2 to the power m. CTR DIVm states the cycle length directly and is used for non-binary counters such as decade counters.
- 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) · SN74HC163 — synchronous binary counters
IEC · Rectangular element with CTRm qualifier, common-control block and weighted outputs
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. The counterpart is the matching functional concept; no equivalence of every detailed standard graphic is asserted.
Shown as an independently authored educational illustration. Use the cited publication and drawing legend to verify the required drafting form.
Schematic · CTR4
What it represents
The general qualifier CTRm identifies a counter with m bits and a cycle length of 2 to the power m. In IEC form the clock appears as C with a + to show counting up, and load, clear and enable inputs use dependency notation such as M1 for load mode and G for count enable. Outputs carry binary weights 1, 2, 4 and 8.
A reader should identify the synchronous and asynchronous inputs from their prefixes, then find the carry output, often labelled CT=15, used to cascade stages. On control drawings counters represent event totals, batch counts or divide-by-n timing.
The symbol does not state maximum count rate or whether the clear is synchronous, except through dependency labels. Read the prefixes carefully.
How to read it
- CTRm gives the bit count; the cycle is 2 to the power m.
- CT=15 marks the terminal-count output used for cascading.
Information to show or reference
- State the bit count in the qualifier.
- Label load, clear and enable with dependency notation.
- Show cascade connections between stages.
A distinction that matters
CTR DIVm states the cycle length directly and is used for non-binary counters such as decade counters.
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)
Lists CTRm and related counter qualifiers and the contents output CT=.
SN74HC163 — synchronous binary counters
Synchronous binary counter documentation.
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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