Omron CPM1A Quick Response Inputs: DM6628 Configuration Reference

Omron CPM1A Quick Response Inputs and I/O Addressing Reference

The Omron CPM1A is the entry-level fixed-I/O controller in the CP-family lineage and the most common platform used by engineers transitioning from smart relays to true PLCs. It supports online program editing, ladder logic with full BCD/binary literal support, and a flexible memory map that scales into the CJ1 and CS1 architectures. One of its most underused features is the quick response input block, which captures pulses shorter than one scan cycle by latching them in a hardware register until the next I/O refresh.

This reference consolidates the CPM1A memory map, I/O channel allocation rules, DM6628 quick-response configuration, and the supporting CX-Programmer workflow. It is written for first-time CP-family users who need to capture sub-scan pulses (e.g. a magnetic reed switch on a short-travel pneumatic cylinder) without resorting to interrupt task programming.

1. CPM1A Memory Architecture Overview

The CPM1A organises all memory into numbered channels. Each channel holds 16 bits addressed as channel.bit (for example, IR000.06 or 200.07). Three address families matter most for I/O and pulse handling:

The fixed-I/O CPM1A-CPU has hard-wired terminal-to-IR mappings. For example, a 20-point CPU exposes inputs IR000.00 through IR000.11 and outputs IR010.00 through IR011.07. Expansion I/O modules, when used, continue the IR range contiguously based on the rack position. There is no rack/slot/%I/%Q prefix in CX-Programmer – engineers simply type the numeric address and the editor resolves it.

2. I/O Channel Allocation Rules (CJ1/CS1 Scaling)

Although the CPM1A has fixed I/O, the same allocation logic is used by the larger CJ1 and CS1 PLCs, where plug-in I/O cards can be remapped to any starting channel. Understanding the rule now prevents confusion when the user later migrates to modular hardware.

2.1 Bit-width per card

2.2 Allocation example (CJ1 rack starting at channel 0)

To address bit 10 of the third card's first channel (i.e. IR00003.10), type 310 into a contact in CX-Programmer. The editor interprets the value as channel.bit by splitting 310 into channel 31 and bit 0; for a 64-point card the same numeric shorthand continues into subsequent channels. For larger controllers the rack number itself becomes the first digit, so 0310 means rack 0, channel 310.

3. BCD and Binary Literals in CX-Programmer

CX-Programmer distinguishes literal number bases with a prefix character on the constant value:

The compare ladder instruction > with operands D2010 (DM word) and #37 (BCD literal) evaluates true when DM2010 contains the BCD-encoded value 37. Mismatched bases will silently fail at the next BCD instruction in the chain, so always match the prefix to the source word's encoding.

4. Quick Response Inputs: Functional Principle

Every CPU scan consists of four phases: I/O refresh → program execution → housekeeping → end-of-task. A pulse shorter than one scan time may arrive and depart entirely between two refreshes, so the program never sees the rising edge. Quick response inputs solve this by hardware-latching the pulse in a flip-flop that is independent of scan timing.

The latch holds the bit high until the next I/O refresh at end-of-scan, at which point it is cleared. This guarantees that the program sees the rising edge on the next execution pass. Important constraints:

• The mechanism is a pulse stretcher, not a true high-speed counter. It does not speed up program execution – it merely guarantees that a sub-scan pulse is captured.
• It is intended for single short pulses, not trains of pulses faster than the scan rate.
• If the requirement is counting pulse frequency or quadrature, use the dedicated high-speed counter inputs and a CTBL/INI/HSCR instruction set instead.

5. CPM1A Quick Response Input Allocations

On the CPM1A, quick response capability is reserved for IR00003 through IR00006. That is, only bits IR000.03, IR000.04, IR000.05, and IR000.06 are hardware-eligible. Each of these four points is mapped to the corresponding physical input terminal on the CPU; the CPM1A's fixed input mapping means you do not have to assign which terminal is fast – the mapping is fixed by hardware.

6. DM6628 Configuration Procedure

DM6628 is a 16-bit Setup Area word that enables quick response and interrupt inputs. By default, after a power-on memory clear, every bit is 0, meaning the four inputs run in standard filtered mode.

6.1 Bit map of DM6628 (CPM1A)

6.2 Step-by-step CX-Programmer procedure

1. Connect to the PLC in Online mode. The DM area setup words (DM6600–DM6655) are read/write only while online or after a Stop-mode transfer; offline they cannot be edited in the PLC.
2. In the project tree, expand PLC → Setup → PLC Setup. CX-Programmer displays the setup table editor.
3. Navigate to address DM6628. The default value displayed is 0000 (all bits zero).
4. To enable quick response on IR000.06 only, write the literal 0010 0000 0000 0000 (binary), which is #1000 BCD or &64 decimal in CX-Programmer notation (the constant #64 or &64 turns bit 06 on).
5. To enable IR000.05 and IR000.06 together, write 0001 1000 0000 0000 binary → bits 05 and 06 set. The decimal value is 96; in BCD notation #96; in binary notation &96.
6. Click Transfer to PLC. The PLC must be in Program (Stop) mode for Setup Area writes from CX-Programmer – some firmware revisions also permit Monitor-mode writes with confirmation.
7. Switch back to Run or Monitor mode and verify the value persisted by reading DM6628 back from the CPU.

6.3 Verification ladder (optional diagnostic)

|  IR000.06       OUT     200.07
|  |--||----------( )-----|  (captured pulse indicator)
|
|  TIM0001    #5
|  |--(T)------------------ (5 s auto-clear of indicator)

Latch bit 200.07 when the quick-response input fires, then auto-reset via a 100 ms × 5 TIM to keep the indicator on long enough for a human to see.

7. Input Constant Filter (DM6620)

DM6620 controls the 8 ms hardware filter applied to inputs that are not in quick-response mode. For inputs 0–7 of IR000, bits 00–07 select the input; setting the corresponding bit to 1 forces a 1 ms filter instead of 8 ms. For quick-response inputs this filter is bypassed – the hardware latch responds to the bare electrical edge.

8. Interrupt Inputs vs Quick Response Inputs

Both feature sets share DM6628 but serve different purposes. Choose correctly or you will lose the timing guarantee you are trying to achieve.

9. Application: Robotic Arm Retract on Plastic Injection Moulder

A common real-world use case is signalling the IMM (Injection Moulding Machine) to close its mould the moment the take-out robot's 1.5 m arm finishes its outward travel. A magnetic reed switch at full extension fires briefly; if the closing signal is generated only after the next scan, the IMM cycle is delayed by one scan period (typically 5–15 ms). With quick response, the bit is reliable; with interrupt, the mould-close contactor can fire sub-millisecond from the edge.

9.1 Ladder example (CX-Programmer)

Step 0001   IR000.06         TIM0001        #3
           |--||-------------( T )-----------|  (300 ms debounce after quick-response latch clears)

Step 0002   TIM0001         OUT  010.00
           |--||------------( )--------------|  (close-mould output to IMM)

Step 0003   IR000.06         OUT  HR00.00
           |--||------------( )--------------|  (retained event log bit)

DM6628 should contain #64 (bit 06 set) before commissioning. Verify by forcing IR000.06 with a screwdriver on the input terminal and watching HR00.00 latch.

10. Online Programming: Why It Matters for the CPM1A

The CPM1A supports online editing while the PLC is in Monitor mode – you can modify contacts, coils, and TIM/CNT preset values without stopping the controller. Edits are buffered and applied at end-of-task. This single feature is often the differentiator when selecting a micro-PLC:

Online editing eliminates the download/restart cycle that lengthens commissioning. For a CPM1A retro-fit on a running machine, this is often the only way to tune TIM presets without shutting down the line.

11. CX-Programmer Productivity Shortcuts

Beyond quick response, CX-Programmer's keyboard-driven workflow is one of the fastest in any PLC IDE. Recommended mappings (Tools → Options → Keyboard Mapping):

Pressing F2 then typing 6 inserts IR000.06 as a contact. The numeric shorthand is the same one used in addressing on the CJ1/CS1 platforms, so muscle memory transfers between controllers.

12. Troubleshooting Matrix

13. Field Commissioning Checklist

1. Document the target scan time before connecting any quick-response input. CX-Programmer displays it in the status bar of an online connection.
2. Confirm DM6620 filter bits are at default (0) for inputs that will use quick response.
3. Write DM6628 with the desired bit pattern while the PLC is in Program mode.
4. From a known clean state, force the input with a test pulse generator and confirm the corresponding IR bit sets.
5. Verify the latch clears on the next I/O refresh by watching the bit transition back to 0 within one scan.
6. Back up the Setup Area to disk via PLC → Transfer → From PLC so the values can be restored on a memory clear.

14. Document References

• Omron CPM1A Operation Manual (Cat. No. W451) – memory map and DM Setup Area definitions.
• Omron CX-Programmer Operation Manual (Cat. No. W446) – Setup editor, online transfer, keyboard mapping.
• Omron CX-One / CX-Programmer Version 4.x Setup Manual – installation, USB serial converter notes, controller-link configuration.
• Omron CP1L Operation Manual (Cat. No. W462) – successor platform with extended quick-response and interrupt input ranges.

All manuals are available from the Omron Industrial Automation website (ia.omron.com) and the regional support portal. Always verify the manual revision matches the CPU's lot/serial number suffix before applying DM6628 settings.