The Q04UDVCPU is Mitsubishi Electric’s 4,000-step Universal V model CPU for the MELSEC-Q programmable controller series, bridging the gap between the entry-level Q03UDVCPU and the mid-range Universal Enhanced models with a modest increase in program capacity while retaining the same high-speed 1.0 ns execution engine and dual built-in Ethernet and USB interfaces. Designed for machine builders and system integrators who require slightly more program space than the Q03UDVCPU without the additional cost of a full Universal Enhanced model, the Q04UDVCPU is a practical choice for multi-axis conveyor control, robotic cell integration interfaces, and distributed I/O master stations. Atlantech Drives holds stock of the Q04UDVCPU. Contact us for fast worldwide delivery and competitive pricing.
What Is the Q04UDVCPU?
The Q04UDVCPU is a member of Mitsubishi Electric’s MELSEC-Q Universal V model CPU family, sharing the same physical form factor, communication interfaces, and base unit compatibility as all other MELSEC-Q Universal CPUs. The 4,000-step program capacity makes it the second smallest in the Universal V model range, positioned directly above the Q03UDVCPU. Like all Universal model CPUs, the Q04UDVCPU processes both sequence control and data handling instructions at 1.0 ns per basic instruction, eliminating the scan time variability associated with older MELSEC-Q H-model CPUs. The module supports structured programming in GX Works2 and GX Works3, including function block (FB) and structured text (ST) programming alongside traditional ladder and SFC.
Key Technical Specifications
- Model: Q04UDVCPU
- Series: MELSEC-Q Universal V model
- Program Memory: 4,000 steps
- Execution Speed: 1.0 ns per LD instruction
- I/O Points: Up to 4,096 (local)
- Built-in Interfaces: Ethernet (100BASE-TX), USB (mini-B)
- Number of Mountable Modules: Up to 64 per base
- Power Supply Voltage: 5 VDC (via base unit)
- Operating Temperature: 0°C to 55°C
- Weight: Approx. 0.17 kg
- Compatible Base Units: Q3B, Q5B, Q6B, Q12B, Q25B, Q32B, Q33B, Q35B, Q38B, Q312B
- Programming Software: GX Works2, GX Works3
Architecture & Design Overview
The Q04UDVCPU implements Mitsubishi Electric’s fourth-generation MELSEC-Q CPU architecture, which separates program execution, I/O refresh, and communication processing into independent internal buses to prevent communication overhead from affecting scan time consistency. The CPU’s internal memory is divided into program memory (4,000 steps), device memory (supporting M, D, T, C, and Z registers at standard capacity), and file register memory (accessible via memory card or internal extended SRAM). The built-in Ethernet port is handled by a dedicated communication processor that operates asynchronously to the main scan cycle, ensuring that Ethernet traffic — whether SLMP polling from a SCADA system or HTTP data logging — does not introduce jitter into the control loop. This architecture makes the Q04UDVCPU suitable for installations where deterministic scan time is a hard requirement, such as servo press controllers or high-speed vision-guided pick-and-place systems.
Expert Tips
When selecting between the Q03UDVCPU and Q04UDVCPU for a new project, calculate the expected compiled program size in GX Works2 before committing to hardware — Mitsubishi’s FB libraries for motion interfaces and communication protocols can consume 500 to 800 steps per function block instance, and a project that appears to fit within 3,000 steps at the design stage may exceed capacity after full FB instantiation. The Q04UDVCPU’s additional 1,000 steps provide a practical safety margin for projects using three or more communication FBs. For systems that will be expanded in the future, note that the Q04UDVCPU does not support program memory extension via SRAM memory card — if memory expansion is a future requirement, specify the Q04UDEHCPU instead, which supports up to 60,000 steps with an optional memory card.
Frequently Asked Questions
Q: Can the Q04UDVCPU replace a Q02UCPU in an existing installation without hardware changes?
A: Yes, the Q04UDVCPU is physically and electrically compatible with all standard MELSEC-Q base units that previously housed a Q02UCPU. The existing I/O, analogue, and communication modules do not need to be changed. However, the program must be re-verified in GX Works2 after the CPU swap, as the Q02UCPU used a different internal device allocation for some special relays and registers. Mitsubishi’s GX Works2 migration wizard can assist in identifying affected instructions.
Q: What happens if the program size exceeds 4,000 steps on the Q04UDVCPU?
A: If the compiled program exceeds the 4,000-step capacity, GX Works2 will display a «Program memory capacity over» error during the write operation and the program will not be transferred to the CPU. The CPU will continue to run the previously loaded program unchanged. The solution is either to optimise the program to reduce step count, upgrade to a Q06UDVCPU or Q13UDVCPU, or restructure FB instances to share common code blocks.
Q: Does the Q04UDVCPU support iQ Sensor Solution (iQSS) for smart sensor integration?
A: The Q04UDVCPU supports iQSS when paired with compatible communication modules such as the QJ71MT91 MODBUS module or CC-Link IE Field master modules. Direct CC-Link IE Field built-in support is available only in the iQ-R series CPUs; for full native iQSS in the MELSEC-Q platform, a dedicated network module is required.
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