Modicon M580 Processors: BMEP58 Models Compared by I/O Capacity and Memory
The BMEP58 processors look alike, but capacity changes a lot between them. Local I/O doubles from the BMEP581020 to the BMEP582040, and doubles again on the BMEP584040. The entry model also has no remote I/O scanner in its published specs. Match your I/O count and your remote drops before you order.
A dead CPU stops everything. You need to know fast whether the module in your hand will cover your system. This guide compares three common Modicon M580 processors using the published specs.
What Stays the Same
Before the differences, here is what all three share:
- 1 Ethernet service port and 2 Ethernet device-network ports
- USB mini-B port
- Up to 64 distributed pieces of equipment
- 4 GB expandable flash for data storage
- MTBF of 600,000 hours
- Power from the rack (no separate supply)
- Operating range of 0 to 60 °C
So the ports won’t tell you which one you have. The numbers below will.
Modicon M580 Processors Compared
| Spec | BMEP581020 | BMEP582040 | BMEP584040 |
|---|---|---|---|
| Local racks | 4 | 4 | 8 |
| Discrete I/O | 1,024 | 2,048 | 4,096 |
| Analog I/O | 256 | 512 | 1,024 |
| Application-specific channels | 36 | 72 | 144 |
| Program RAM | 4 MB | 8 MB | 16 MB |
| Data RAM | 384 kB | 768 kB | 2,048 kB |
| Speed (65% Boolean + 35% fixed arithmetic) | 7.5 Kinst/ms | 7.5 Kinst/ms | 30 Kinst/ms |
| Remote I/O scanner | Not listed (DIO scanner only) | Yes | Yes |
| Ethernet communication modules supported | 2 | 2 | 4 |
| Current draw at 24 V DC | 270 mA | 295 mA | 295 mA |
Figures come from the published specifications on each product page. Confirm against Schneider’s datasheet for your firmware revision.
1. Count Your Real I/O First
Count the points your program actually uses. Don’t go by the old CPU’s label alone.
- Under 1,024 discrete and 256 analog: any of the three covers it
- Up to 2,048 discrete and 512 analog: the BMEP582040 or BMEP584040
- Above that: only the BMEP584040
Buying under your real count means missing I/O after the swap.
2. Check Whether You Use Remote I/O Drops
This is the check people miss. The BMEP581020’s published specs list a DIO scanner only. They don’t list a remote I/O scanner. The BMEP582040 and BMEP584040 do.
If your CPU runs remote drops today, don’t replace it with the entry model without confirming. Check the datasheet first.
3. Notice That Speed Doesn’t Move Until the Top Model
The BMEP581020 and BMEP582040 post the same instruction speed in the published specs. The BMEP584040 is four times higher. So the mid model buys you capacity, not speed. The top model buys you both.
If your scan time is already tight, that matters more than I/O count.
4. Check the Memory Against Your Project
Program RAM goes from 4 MB to 8 MB to 16 MB. Check your project’s size in the programming software. A large project that fit before may not fit in a smaller CPU.
5. Buy a Processor That Has Been Tested
Ask whether the CPU has been powered up and run, not just visually checked. Ask what firmware it carries, since firmware has to work with your project.
Browse the full Modicon M580 category for tested stock. For exact specs by revision, Schneider Electric’s own Modicon M580 documentation is the best source.
Frequently Asked Questions
Q: Can I replace a BMEP582040 with a BMEP584040? A: The larger CPU has more capacity, so it can cover the same system. But the application still has to be loaded and checked on the new CPU. Confirm firmware and project compatibility first.
Q: Does the BMEP581020 support remote I/O drops? A: Its published specs list a DIO scanner only, with no remote I/O scanner. If you rely on remote drops, confirm against the datasheet before ordering.
Q: How many local racks can each processor handle? A: The BMEP581020 and BMEP582040 each handle 4 local racks. The BMEP584040 handles 8.
Q: How much power does the processor draw? A: It’s powered from the rack. The published draw is 270 mA at 24 V DC for the BMEP581020 and 295 mA for the other two.
Matching Modicon M580 processors comes down to four numbers: I/O count, remote I/O needs, memory, and speed. Check all four against the table above, and buy from a supplier that tests before it ships.
