Why Does the ET 200SP HA DI 16x24VDC Module Use Four Input Bytes?

The Siemens ET 200SP HA module 6DL1131-6BH00-0PH1 uses four input bytes because its 16 digital values occupy two bytes and their per-channel value status (QI) occupies two more. The extra bytes are quality information, not spare process inputs. If time stamping is configured, the documented address space also includes 18 bytes of timestamp data, so check the complete configured mapping before assigning adjacent addresses.

Address Mapping

For the module's normal address-space mapping, the Siemens device manual assigns the bytes as follows:

Input byteContentsIB x + 0Digital inputs DI0–DI7IB x + 1Digital inputs DI8–DI15IB x + 2Value status QDI0–QDI7IB x + 3Value status QDI8–QDI15

Here, x is the module's configured start address. Each QI bit corresponds to one digital channel.

How to Interpret QI

The module manual defines value status 1 as good and 0 as bad. A bad status indicates that the digital value cannot be output because of an error or that the channel is deactivated. The manual also notes that a wire break does not set value status to bad when wire-break testing is disabled; QI therefore must not be treated as a substitute for every enabled channel diagnostic.

PCS 7 Driver Considerations

The forum discussion reports that the PCS 7 CFC driver wizard connects quality information through ProImQB and a selected quality bit. That integration depends on the installed driver library and project configuration. The cited module manual establishes the hardware address mapping, but does not establish that a particular CFC project has automatically connected every channel. Inspect the generated driver connections and the configured start address in the actual PCS 7 project.

Time-Stamp Address Space

When 1 ms time stamping is configured, the manual shows DI values at x+0 and x+1, QI at x+2 and x+3, and time information in bytes x+4 through x+21. This additional range matters when checking the next module's assigned addresses. Do not assume the four-byte mapping is the complete footprint when timestamping is enabled.

Verification

In HW Config, confirm the exact module article number and its configured start address. Compare that address range with the module's process and QI mapping, and include the timestamp range if the feature is configured. In CFC, inspect the generated driver connections for the intended channel quality signals. During controlled commissioning, compare a known channel state with its mapped DI bit and inspect its corresponding QI bit; follow the plant's approved test and download controls.

Limitations and Operational Precautions

The byte map applies to article number 6DL1131-6BH00-0PH1 as documented in Siemens manual A5E39265608-AB (11/2017). The ticket does not identify the PCS 7 or APL version, so its statement about automatic ProImQB wiring is not generalized here. Address changes affect I/O mapping; review the full hardware configuration and operating impact before downloading.

Engineer FAQ

Are bytes x+2 and x+3 spare inputs? No. They carry the 16 channels' value-status bits.

Is QI equivalent to wire-break diagnosis? No. The module manual explicitly qualifies QI behavior when wire-break testing is disabled.

Does the timestamp feature reuse the QI bytes? No. The documented map retains QI at x+2 and x+3, then assigns timestamp data at x+4 through x+21.

Technical References

Siemens, Digital Input Module DI 16x24VDC HA (6DL1131-6BH00-0PH1), Manual 11/2017, A5E39265608-AB, §§A.6–A.7: https://cache.industry.siemens.com/dl/files/249/109747249/att_921200/v1/et200sp_ha_di_16x24vdc_manual_en-US_en-US.pdf