New PLC Mitsubishi FX3U-64MR ES-A Programmable Logic Controller OEM

Mitsubishi FX3U-64MR/ES-A | MELSEC-F Series PLC Main Unit — 64 I/O, 32 DI / 32 Relay DO, 100–240VAC, 64K Steps, 65ns, RS-422, DIN Rail, 220×90×86mm

Overview

The Mitsubishi FX3U-64MR/ES-A is the 64-point relay output variant of the MELSEC FX3U — Mitsubishi's top-tier compact PLC series. Everything needed for a complete controller sits in a single housing: the wide-range AC power supply, the CPU, the input circuitry for 32 channels, and the relay output stage for another 32.

There is no separate power supply module to specify or wire. On the DIN rail, the FX3U-64MR/ES-A occupies 220mm — wide by compact PLC standards, but the trade-off is a machine-ready controller that comes pre-assembled with all basics integrated.

The "ES" suffix identifies the European specification, and the "-A" further designates this as the standard AC supply version. The relay output type (R) makes it the most field-wiring-versatile option in the FX3U-64 range: each relay contact is potential-free and can switch AC or DC loads at up to 240VAC or 30VDC, up to 2A per point.

Different output channels can switch entirely different voltage levels — one channel powers a 230VAC indicator lamp, another switches 24VDC to a solenoid coil, a third drives a 48VDC motor starter coil. This load independence per output is what makes relay-output PLCs the preferred choice for panels mixing multiple voltage rails.

At 65ns per basic instruction, the FX3U CPU is faster than most controllers in its class — a legacy of Mitsubishi's MELSEC engineering discipline that prioritises scan cycle performance. For a 64-point machine with a moderate programme of 3,000–5,000 ladder steps, the scan cycle comfortably runs below 3ms, which is fast enough for the sequencing, interlocking, and timer-based control that defines the FX3U's target applications.

Key Specifications

64K Steps — Programme Capacity in Context

The 64,000-step programme memory of the FX3U-64MR/ES-A represents a substantial step up from the FX3G and FX3S families. In practical terms: a typical discrete machine control programme — 50 rungs of interlocking logic, 20 timer routines, 15 counter sequences, 10 HMI data move instructions, and 5 communication exchange routines — occupies roughly 3,000 to 6,000 steps.

The FX3U's 64K programme memory can accommodate ten times that, leaving room for expanded machine variants, process logging routines, and communication handling without architectural changes.

The programme is held in battery-backed RAM during normal operation. For applications where battery maintenance is unacceptable or where the programme must survive extended storage, a Flash ROM memory cassette (FX3U-FLROM-64L) installs directly into the CPU's front-panel cassette socket.

When the cassette is installed, the CPU uses the cassette's programme instead of internal RAM — the cassette retains data without a battery, with a retention guarantee measured in decades.

Relay Outputs — Versatility and Limitations

Relay contacts have physical advantages and physical limits. The advantage is electrical universality: an NC relay contact cares nothing about what voltage or current type it switches — AC, DC, 24V, 48V, 230V, low-frequency signals, and resistive or moderately inductive loads all pass through the same contact mechanism.

The limitation is switching speed: relay contacts take 10ms to operate (the FX3U specification) and cannot be toggled faster than a few Hz without accelerating contact wear.

For outputs that need to switch at speeds approaching or exceeding 10ms — stepper drive pulse trains, PWM signals, high-speed digital outputs to servo amplifiers — the relay-output FX3U-64MR is not the right choice.

The transistor-output variants (FX3U-64MT for NPN or FX3U-64MT/ESS for NPN source-type) switch in microseconds and handle output frequencies up to 100kHz.

The practical selection rule: relay outputs for 32 DO or fewer channels switching infrequently (contactors, solenoids, pilot lights, alarm horns); transistor outputs when any channel must switch faster than 10ms or drive a pulse-based device.

Expansion Architecture — Beyond 64 Points

The FX3U-64MR/ES-A starts at 64 I/O points but is not confined to them. Up to 24 expansion I/O modules (FX2N and FX3U series) connect to the right side of the main unit through direct bus connectors — no wiring, no cable, just module-to-module connection.

These expansion modules add digital inputs, digital outputs (relay or transistor), analog inputs, analog outputs, and specialty I/O in standard 8- or 16-channel increments. 

The total local I/O addressable by the CPU reaches 256 points.

Beyond local expansion, the FX3U communicates with remote I/O via CC-Link (using the FX3U-32CCL or FX3U-CCLIEF special function modules), extending the effective I/O count to 384 points total.

Each special function module slot also accepts positioning modules (FX3U-1PG, FX3U-2HC), serial communication modules (FX3U-232-BD, FX3U-485-BD), temperature controllers (FX3U-4AD-TC), and Ethernet adapters. The result is a controller that grows with the machine requirement without platform migration.

FAQ

Q1: What is the difference between FX3U-64MR/ES and FX3U-64MR/ES-A?

The ES-A suffix designates the standard AC power supply version with 100–240VAC input. The ES (without -A) is functionally identical in most markets.

The "-A" designation was added in certain product documentation to distinguish the standard AC unit from optional DC-supply or special-export variants. 

For practical purposes, ES and ES-A are interchangeable in the same application. Always confirm the power supply input specification on the physical unit label before replacing.

Q2: Can the FX3U-64MR/ES-A communicate with Mitsubishi servo amplifiers directly?

Not directly via the RS-422 port alone. For direct high-speed servo communication, the FX3U requires either the FX3U-10PG or FX3U-20SSC-H positioning modules for pulse-train or SSCNETIII fibre-optic servo connection.

The standard RS-422 port supports RS-232/RS-485 serial communication to HMI panels, inverters (via RS-485 with Mitsubishi FR series), barcode readers, and PC interfaces — not servo axis control.

For complete servo axis control, specify the appropriate positioning module alongside the main unit.

Q3: Does the FX3U-64MR/ES-A have a built-in real-time clock, and is it retained during power loss?

Yes, the FX3U CPU includes an integrated real-time clock (RTC) with calendar and time-of-day function accessible from the ladder programme.

The RTC is retained during power loss by the internal lithium battery. Battery life is typically 5–6 years at 25°C ambient. 

When the battery voltage drops below threshold, the FX3U sets a low-battery flag in a special relay (M8005 and M8006 in FX3U notation), which the programme can use to trigger a maintenance alarm before the battery fails completely.

Q4: Is the FX3U-64MR/ES-A compatible with GX Works2 and GX Works3 programming software?

The FX3U is natively supported by GX Works2 (the current programming software for FX3U and other MELSEC PLC families).

GX Works3 is Mitsubishi's next-generation engineering environment targeting the iQ-R and iQ-F series — it does not support FX3U programming. 

For new FX3U projects, use GX Works2.

For new projects that may expand to iQ-R or iQ-F in the future, consider specifying the FX5U (iQ-F) instead, as it is programmable in GX Works3 and provides a smoother migration path.

Q5: What is the maximum high-speed counter input frequency, and which inputs are dedicated?

The FX3U CPU includes 6 high-speed counter channels (C235 to C255 in the device table), with maximum input frequencies of up to 100kHz for single-phase and 50kHz for phase-difference (A/B quadrature) counting.

The high-speed counter inputs are allocated to specific input terminals (X000 through X007 depending on configuration).

These terminals are hardware-interrupt driven — they count independently of the CPU scan cycle, ensuring no pulse loss even during longer scan cycles. 

For standard inputs (X008 and above), the scan-cycle-based input filter applies, with a default filter time of 10ms adjustable down to 0ms for faster response.