Troubleshooting Data Transfer from N Register N61:131 to N61:147 into Memory Location ST252:0

Jimtech67 mentioned that all the data in the N registers is in ASCII format and has been successfully sent to a printer for years. Now, the goal is to display a portion of this data in AdvancedHMI software by converting it to an ST file format. Converting the data to Integers in the SLC-5/03 would make the transfer to a string in Visual Basic or C# within AdvancedHMI easier than attempting it in ladder logic in the SLC. It is interesting to note that despite STNNN.Y.DATA containing an array of 16-bit integers, CPW cannot be used to transfer data from this N-file. While observing an older post where CPW was used (referenced in Post #2), the assumption was that with a more advanced version of RSLogix 500, it might be possible. However, working with the freebie RSLogix Micro Starter Lite, there may be a workaround involving overwriting to an indirect address to circumvent the file boundary limitations.

• 27-09-2024
• drbitboy

Believe it or not, achieving this is possible even in Micro Starter Lite by utilizing indirect addressing in the Destination file address parameter when using the COPy instruction. By doing this, the compiler remains unaware that the COPy instruction is writing beyond the N-file boundary (for example, N9) and instead writes into the ST-file (for example, ST10). As Jouni Rynö put it, "It's all just zeros and ones; it can't be that difficult." It is important to note that in the image below, the value of N7:0 is 3, which serves as the indirect address for the start of the string ST10:0.

• 27-09-2024
• drbitboy

When is the transfer of data to the ST10:0.DATA[0] registers initiated? Am I overlooking a crucial step in this process?

• 28-09-2024
• jimtech67

In programming, memory is divided into various data types, such as strings and integers. The address reference ST10:0 points to a memory structure containing a string data type composed of 42 16-bit words. The first word stores the length of the string (ST10:0.LEN), while the subsequent words hold the characters of the string in pairs. Each word represents two characters, with the high 8 bits representing the ASCII code of the first character and the low 8 bits representing the ASCII code of the second character. On the other hand, the N9 file only consists of three elements (N9:0, N9:1, N9:2). Any elements beyond N9:2 do not actually exist in the file. However, using the address reference N9:[N7:0], where N7:0 > 2, will extend beyond the boundaries of the N9 file and into the ST10 file, which follows the N9 file in memory. When N7:0 is 3, N9:[N7:0] points to the same register as ST10:0.LEN. Subsequent memory addresses, such as N9:[N7:0 + 1] and N9:[N7:0 + 2], correspond to ST10:0.DATA[0] and ST10:0.DATA[1] respectively.

• 28-09-2024
• drbitboy

drbitboy mentioned that when referencing the address N9:[N7:0] where N7:0 is greater than 2, it will extend beyond the boundaries of the N9 file and into the ST10, the String-file located after the N9 file in memory. However, this will only hold true if no additional elements are added to N9.

• 28-09-2024
• ASF

Copying in programmable logic controllers (PLCs) uses the destination data type to determine the length of the copy, not the source. During testing with random number data, it was observed that the copied data was moved from the N file to the string file. To ensure accurate copying, the string length needs to be staged within the data, as demonstrated when N7:0 was copied into ST19:2.LEN.

• 28-09-2024
• Christoff84

ASF warned against adding more elements to N9 in order to avoid potential issues. It is also important to note that the Length parameter in the COP command and the offline value of N7:0 should not be altered. This is because in offline mode, if N9 has fewer elements than the sum of the length parameter and the offline value of N7:0, RSLogix will resize N9 to that length. A suggestion would be to resize N9 to have a total of 256 elements to prevent any complications.

• 28-09-2024
• drbitboy

Christoff84 mentioned that the COP instruction in RSLogix 500 uses the destination data type to determine the length of the copy, not the source. Testing with random number data showed that the copy was made from the N file to the string file. To ensure the correct length is copied, it is necessary to include the string length in the data. When using the previous N-file as a proxy for the ST-file, both the starting address and the length parameter are based on the N-file elements. Consider using CPW instead to ensure the number of words copied is accurate, even if the source and destination data types differ. If experiencing issues verifying this, it may be due to the version of RSLogix 500 being used.

• 28-09-2024
• drbitboy

In a discussion about programming with RSLogix 500, drbitboy mentioned a potential issue when using a previous N-file as a proxy for the ST-file in ladder logic programming. This can result in the Dest starting indirect address being interpreted as an offset from a different file than intended, leading to discrepancies in the Length parameter for the COP instruction. An alternative suggestion is to use CPW, where the Length parameter specifies the number of words copied and allows for different data types between the Source and Dest. The version of RSLogix 500 being used, in this case, is v12. Testing on a SLC 5/04 versus a 5/03 may also impact the outcome. It is recommended to ensure the N7 file is at least 43 words long to avoid potential issues.

• 28-09-2024
• Christoff84

In a forum post, Christoff84 explains troubleshooting a compatibility issue with v12 software on a SLC 5/04 due to lack of a 5/03 model for testing. The length of the N7 file, at least 43 words, may also play a role. In RSLogix Micro Starter Lite/MicroLogix 1100 systems, the COP command requires Source and Dest operands to be the same data type, whereas CPW does not. Both operands must be offsets into an N-file. Despite meeting these requirements, certain cases may still not function properly. The N7 file typically consists of 256 elements. This situation presents a challenging problem for users.

• 28-09-2024
• drbitboy

User drbitboy mentioned that in RSLogix Micro Starter Lite/MicroLogix 1100 systems, the Source and Dest operands must be the same data type for the COP instruction, but not for the CPW instruction. This means that if the Source is an offset into an N-file, the Dest also needs to be an offset into an N-file for the COP instruction to work properly. Despite this, there are instances where expected functionality does not occur. The N7 file consists of 256 elements or words. This discrepancy can be puzzling. However, the issue is not with the RSLogix version itself, but rather with the limitations of the Lite version restricting testing capabilities. The problem you are encountering is specific to the MicroLogix compared to the SLC 5 series. It is worth noting that CPW is only supported by MicroLogix processors, except for the MicroLogix 1000. For more information, refer to the instruction help for both the CPW and COP instructions. The CPW instruction indicates that strings are supported in MicroLogix 1400 series B controllers, while the COP instruction specifies that strings are only supported in specific 5/03, 5/04, and 5/05 processors.

• 28-09-2024
• MikeyN

A user named jimtech67 mentioned about using a SLC 500 5/03 and provided a helpful link to Rockwell Automation's support page. The issue involves converting data from an Integer (N) file to a String (ST) file. It is worth noting that all data in the N registers is in ASCII format and has been successfully sent to a printer for years. In order to display a small portion of this data in AdvancedHMI software, it needs to be converted to a ST file format. While C-More software allows flexibility in designating N registers as any data type, for SLC 5/03, 04, 05 PLCs, a specific technote (ID: QA2284) is needed. The COP instruction can be used, but the Length parameter must be set to 1 and the first element of the N file should indicate the length of the string. There seems to be an error in the example provided by Rockwell Automation, as they show a length of 3 instead of 1 in the COP instruction. To resolve this issue, refer to the appropriate technote for SLC 5/03, 04, 05 PLCs and make necessary adjustments as per the instructions provided. This will ensure correct data conversion and display in the AdvancedHMI software. Thank you to everyone for their assistance and input on this matter.

• 28-09-2024
• OkiePC

Thank you for the assistance in getting everything to work properly with B253/1. Initially, I utilized a buffer to account for the print control commands within the full length of the string. I had concerns about how Advanced HMI would manage this, but it displayed the name as desired. Subsequently, I used the full-length string (as used for printing) with no issue on the Advanced HMI display. However, I later discovered that the control characters were not being ignored. This was due to the string not being long enough, causing the line return and line feed to disrupt the text alignment. Please note that the first word of the COPY function indicates the length of the string.

• 28-09-2024
• jimtech67