The Q00UCPU is Mitsubishi Electric’s 8,000-step Universal model CPU for the MELSEC-Q programmable controller series — the entry-level Universal model CPU in the Q-series range, providing 8,000 steps of program memory with 34 ns per basic instruction execution speed, USB programming interface, and Q-series base unit compatibility for building compact MELSEC-Q control systems where program capacity of 8,000 steps meets the application’s control requirements at the lowest cost entry point in the Universal CPU range. In stock at Atlantech Drives. Request your quote within 24-48 hours with worldwide shipping and 12-month warranty.
What Is the Q00UCPU?
The Q00UCPU is a MELSEC-Q series Universal model CPU module providing 8,000 steps of program memory — the smallest program capacity in the Universal CPU lineup, below the Q02UCPU (20,000 steps) and Q03UDECPU (30,000 steps with built-in Ethernet). The «U» designation identifies the Universal model generation — providing the same 34 ns per basic instruction execution speed as all Universal CPUs, substantially faster than the legacy Basic model CPUs (Q00CPU, Q01CPU) while maintaining backward compatibility with the Q-series base unit infrastructure. The Q00UCPU installs in the CPU slot (slot 0) of any Q-series main base unit and is compatible with all Q-series I/O modules (QX80, QY40P, etc.) and intelligent function modules (QJ71E71-100 Ethernet, QD75MH4 positioning, etc.) — the same module ecosystem as the higher-capacity Q02UCPU, Q03UDECPU, and Q04UDEHCPU. Despite the smaller program memory, the Q00UCPU provides the same device memory capacity as the Q02UCPU for internal relay (M), data register (D), timer (T), and counter (C) devices, making it appropriate for applications where the control logic is compact but the data storage requirement (D register count for recipes, production data, setpoints) is similar to a 20,000-step application. The Q00UCPU includes a USB Type-B port for direct GX Works2 programming connection and an RS-232C port for legacy serial programming or communication applications.
Key Technical Specifications
- Model: Q00UCPU
- CPU Type: Universal model
- Program Memory: 8,000 steps
- Basic Instruction Execution Time: 34 ns per step
- Device Memory: Internal relay (M): 8,192 points; Data register (D): 12,288 points; Timer (T): 2,048 points; Counter (C): 1,024 points
- I/O Points (Max): 4,096 (with extension base units)
- Programming Interface: USB Type-B, RS-232C (9-pin D-Sub)
- Memory Card: Not supported
- Compatible Base Units: Q3□B, Q5□B, Q6□B, Q3DB main base units
- Power Consumption: 5 VDC internal bus, approx. 0.47 A
- Operating Temperature: 0°C to 55°C
- Dimensions (W × H × D): 27.4 mm × 98 mm × 89.3 mm
- Weight: Approx. 0.18 kg
Series Comparison & Selection Guide
Within the MELSEC-Q Universal model CPU range, the Q00UCPU provides the minimum program capacity (8,000 steps) at the lowest cost — appropriate when the complete machine control program fits within 8,000 steps and no additional capacity is anticipated. The next model up, the Q02UCPU (20,000 steps), provides 2.5× more program capacity for a moderate cost premium — specifying the Q02UCPU provides substantially more headroom for future program additions, debugging routines, and extended alarm text without risking capacity exhaustion. For applications near the 8,000-step boundary, the Q02UCPU is the safer specification — running out of program memory during a machine’s service life requires CPU module replacement (disrupting production for the upgrade) and is a higher-cost event than the initial cost difference between Q00UCPU and Q02UCPU. The Q00UCPU is correctly specified when the control program is definitively simple — a single conveyor zone controller, a basic pump station sequencer, a single-axis step motor controller, or a simple machine with limited interlocks — and program growth is not anticipated. When comparing Q00UCPU to the older Q00CPU Basic model: the Q00UCPU provides 34 ns per instruction (versus 160 ns for Q00CPU), more device memory, and USB programming port — significant capability improvements at the same price point, making the Q00UCPU the recommended specification for all new Q-series designs regardless of program size requirement.
Installation Advice
The Q00UCPU’s 8,000-step program limit makes program memory management more critical than in higher-capacity CPU models — monitor the used step count in GX Works2’s program capacity display (online > PLC information > Program Memory Usage) during development and leave at least 20% free capacity (1,600 steps) for debugging routines, temporary test logic, and future minor program additions. If program memory approaches 90% during commissioning, plan a CPU upgrade to Q02UCPU before the machine is released to production — a field CPU upgrade after machine acceptance is more disruptive than specifying the Q02UCPU initially. For the Q00UCPU’s battery replacement (Q6BAT or Q7BAT), note that the Q00UCPU provides program memory retention from the battery when the PLC is powered off — unlike some PLCs with flash-based program storage, the Q00UCPU’s program is held in battery-backed RAM and is lost if the battery depletes completely with the PLC powered off for an extended period. Replace the battery every 5 years and immediately when the BAT LED illuminates — do not wait for the next scheduled maintenance if the battery warning activates. For GX Works2 USB programming connection to the Q00UCPU, use a USB Type-B cable (standard printer cable type) — verify the USB driver for the Q00UCPU is installed on the engineering workstation from Mitsubishi’s FA library before the first connection attempt.
Frequently Asked Questions
Q: Can the Q00UCPU be upgraded to Q02UCPU simply by swapping the CPU module without changing the base unit or other modules?
A: Yes. The Q00UCPU and Q02UCPU are physically identical in width (27.4 mm) and use the same Q-series bus connector — swapping the CPU module while retaining the existing base unit, power supply, and all other modules requires only writing the existing GX Works2 program (backed up before the swap) to the new Q02UCPU. No hardware changes to the base unit or other modules are required. After CPU replacement, verify the I/O module assignment in GX Works2 online to confirm all modules are correctly detected with the new CPU before resuming production.
Q: Does the Q00UCPU support multi-CPU configuration with a Q172DSCPU motion CPU?
A: The Q00UCPU has only one CPU slot (slot 0) in Q-series main base units — multi-CPU configuration requires a base unit with multiple CPU-capable slots (Q38B, Q312B) and a CPU module that supports multi-CPU operation. The Q00UCPU does support multi-CPU operation in theory, but the Q35B (the most common small base unit for Q00UCPU systems) has only one CPU slot, limiting Q35B systems to single-CPU operation. For multi-CPU servo systems (Q02UCPU + Q172DSCPU), the Q38B or Q312B must be specified as the main base unit.
Q: What is the Q00UCPU’s scan time for an 8,000-step program, and is it adequate for standard machine control?
A: At 34 ns per basic instruction and 8,000 steps, program execution takes approximately 0.27 ms plus I/O refresh and communication overhead — typical total scan time with a full module complement in a Q35B (3 I/O modules) is approximately 1–3 ms. This scan time is fully adequate for standard machine sequence control, conveyor systems, and pump station control. For high-speed I/O requiring sub-millisecond response, the Q00UCPU’s interrupt function provides sub-scan response to critical input events without waiting for the complete scan cycle.
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