Formula Used
Vertical channel length = max(0, min(A right, B right) - max(A left, B left)).
Horizontal channel length = max(0, min(A top, B top) - max(A bottom, B bottom)).
Adjusted length = raw channel length + 2 × end extension.
Pitch gridded length = ceil(adjusted length ÷ routing pitch) × routing pitch.
Final planning length = gridded length + detour adders + bend penalty adders.
Effective channel width = physical channel gap + 2 × clearance.
Available tracks = floor(effective channel width ÷ routing pitch).
Estimated area = final planning length × effective channel width.
How to Use This Calculator
- Enter both macro names for clear exported results.
- Enter lower-left X and Y coordinates for each block.
- Add width and height for each block.
- Set the coordinate scale to convert input units into microns.
- Choose auto mode or force a routing style.
- Add routing pitch, clearance, detours, and bend penalties.
- Press calculate to show results above the form.
- Use CSV or PDF export for design review notes.
Example Data Table
| Case |
A X,Y,W,H |
B X,Y,W,H |
Pitch |
Expected Reading |
| Vertical shared projection |
0, 0, 120, 80 |
20, 120, 100, 70 |
0.28 |
Uses X overlap as channel length. |
| Horizontal shared projection |
0, 0, 90, 120 |
130, 20, 70, 80 |
0.32 |
Uses Y overlap as channel length. |
| Diagonal placement |
0, 0, 80, 80 |
130, 130, 60, 60 |
0.40 |
Uses Manhattan fallback in auto mode. |
Channel Length Planning in Floorplan Work
Channel length is an early routing estimate. It helps a layout team judge whether two blocks can share a clean routing corridor. In a floorplan, the useful length is normally taken from the shared projection of two nearby macros. A vertical channel uses the horizontal overlap. A horizontal channel uses the vertical overlap. This calculator follows that idea, then adds practical routing details.
Why the Number Matters
A small channel can force congestion. A long channel can waste silicon area. The best value depends on macro size, spacing, pin demand, and routing pitch. Early estimates do not replace detailed routing. They guide placement before the design becomes expensive to change. A planner can compare options quickly. Wider spacing can increase track count. Better alignment can increase usable channel length.
Advanced Options
The form accepts lower-left coordinates, block width, and block height. It can detect vertical, horizontal, diagonal, or overlapping relationships. When blocks do not share a direct projection, the tool also reports center based routing distances. Scale converts database units into microns. Pitch rounds the planned route to a track grid. Detour length and bend penalty represent jogs around blockages, feedthroughs, or reserved power regions. End extension models extra length near pins.
Reading the Result
The raw channel length is the geometric projection. The adjusted length adds end extension. The gridded length snaps that value to the routing pitch. The final planning length includes detours and bend penalties. The effective channel width adds clearance to the physical gap. Available tracks are estimated from width and pitch. Area estimate multiplies final length by effective width. The status note explains whether the blocks are aligned, separated, diagonal, or overlapping.
Good Use in Design Reviews
Use this calculator during macro placement, chip planning, and routing feasibility checks. Try several placements. Watch how overlap, gap, and pitch affect the result. Export the result for design notes. Keep assumptions visible, because later tools may use different routing rules. A clear estimate helps teams discuss congestion, spacing, and floorplan quality before final implementation. Review the exported values beside placement screenshots for easier communication. Save each case with the block names and chosen technology assumptions before team signoff in reviews too.
FAQs
What is channel length in VLSI floorplanning?
It is the usable routing corridor length between two placed blocks. For vertically separated blocks, it usually follows horizontal overlap. For horizontally separated blocks, it usually follows vertical overlap.
Why does the calculator ask for lower-left coordinates?
Lower-left coordinates define each block boundary. Width and height complete the rectangle. These values let the tool calculate overlap, gap, channel direction, and centerline distances.
What does auto mode do?
Auto mode checks block relation. It selects a vertical channel, horizontal channel, overlap warning, or Manhattan fallback when blocks do not share a direct projection.
Why is routing pitch included?
Routing happens on a grid. Pitch rounds the adjusted channel length to a realistic track multiple. This creates a cleaner planning estimate.
What is end extension?
End extension adds extra length at both channel ends. It can represent pin access, jog space, access regions, or small routing margins.
What is bend penalty?
Bend penalty adds extra equivalent route length for turns. It helps estimate added effort caused by jogs, corners, or non-straight channel paths.
What happens if blocks overlap?
The calculator reports an overlap conflict in auto mode. A real floorplan should resolve that placement issue before using channel estimates.
Can this replace detailed routing tools?
No. It is an early planning calculator. Use it for placement checks, comparison, notes, and quick feasibility review before detailed routing starts.