COMPONENTS / PARAMETER SIZING

PLC I/O Selection

Plan CPU and expansion modules from I/O counts, high-speed counters and network protocols.

Input Parameters

Edit the example values. Results update as you type.

DI · Digital Inputs

DO · Digital Outputs

AI · Analog Inputs

AO · Analog Outputs

High-Speed Counter Channels

The example uses A/B quadrature, requiring two dedicated inputs per channel.

Require PROFINET

Require Modbus TCP

Results

CPU Configuration Approach: CPU + 5 example expansion modules
High-Speed Counting: 1channels
Network Requirements: PROFINET

Formula

Planned I/O = ⌈Required I/O × 1.20⌉ · Modules = ⌈max(0, Planned I/O − Available Onboard I/O) / I/O per Module⌉

Substitution

DI: ⌈18 × 1.20⌉ = 22 points; DO: ⌈12 × 1.20⌉ = 15 points; AI: ⌈4 × 1.20⌉ = 5 points; AO：⌈2 × 1.20⌉ = 3 points

Calculation Steps

Reserve 20% for each I/O type, starting with an example CPU with 14 DI / 10 DO.
Subtract DI reserved for high-speed counters, then calculate expansion using 16-point digital and 4-point analog modules.
Select a CPU or communication module supporting PROFINET; verify controller, device, client or server roles and connection counts.

Result Explanation

Example counts help plan configuration. Verify PNP/NPN, transistor or relay outputs, analog signal types, counting frequency and backplane power against site requirements.

Type	Required / Planned	Usable Onboard	Suggested Expansion
DI	18 / 22	12 points	1 × 16 points
DO	12 / 15	10 points	1 × 16 points
AI	4 / 5	0 points	2 × 4 points
AO	2 / 3	0 points	1 × 4 points

Product Candidates

Parameter-matched candidates

Parameter sizing is available. No model in the current library meets these conditions.

Select actual S7-1200 CPUs and modules →

Formulas and FAQ

Planned points = ⌈required points × 1.20⌉

Can I purchase directly from the example module count?

Verify actual expansion limits, wiring types, protocol roles, backplane power and sampling specifications.