M0/M1 files with a 1746-BAS module

phuz

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I'll admit that in all these years I have only encountered M0/M1 files one other time, and it was used to communicate with Eurodrives.

In a SLC program I am converting to a Logix, there is a BASIC module, but there are no physical connections on it. The program uses M0/M1 files, specifically around block transfers to PV900 terminals. Is it safe to assume that these are just buffers used because of the lack of memory in the SLC (5/04 series C)?
 
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You're correct that the Input and Output address space in the SLC-500 is fairly small; the backplane can handle a maximum of 32 discrete input Words and 32 discrete output words per module.

"Module Files" are a sort of in-the-background block transfer of larger amounts of data to a specialty module in the 1746 platform.

You'll find them used with Prosoft modules, and the BASIC module, and with 1747-SN (RIO Scanner) and 1747-SDN (DeviceNet Scanner) modules.

Reverse-engineering a 1746-BAS application can be tricky. You'll have to get out the user manual and do a listing of the program in the module, and figure out which "CALL xx" functions in the program do what.
 
You're correct that the Input and Output address space in the SLC-500 is fairly small; the backplane can handle a maximum of 32 discrete input Words and 32 discrete output words per module.

"Module Files" are a sort of in-the-background block transfer of larger amounts of data to a specialty module in the 1746 platform.

You'll find them used with Prosoft modules, and the BASIC module, and with 1747-SN (RIO Scanner) and 1747-SDN (DeviceNet Scanner) modules.

Reverse-engineering a 1746-BAS application can be tricky. You'll have to get out the user manual and do a listing of the program in the module, and figure out which "CALL xx" functions in the program do what.

Dang. I don't have the BAS program and I doubt the customer (1.5 hours away) is able to pull it for me. I just assumed they were using the M0/M1 locations for in/out buffers for the PanelViews. I didn't think there would actually be code executing in there since there were no physical RS232/485 connections to the module.
 
To extract a program from a BASIC module you need to connect to its serial console port and perform a LIST command to print the program.

It's theoretically possible to exchange data with the BASIC module for internal calculations that are easier/better done in BASIC52 than in relay ladder logic, but I've never seen it done. I have always seen BASIC modules connected serially to external devices.
 
To extract a program from a BASIC module you need to connect to its serial console port and perform a LIST command to print the program.

It's theoretically possible to exchange data with the BASIC module for internal calculations that are easier/better done in BASIC52 than in relay ladder logic, but I've never seen it done. I have always seen BASIC modules connected serially to external devices.

Same here, but there are no connections in this circumstance.

Yup, I'm familiar with getting the program out, but I'm too far away right now. The customer did send me files that they thought were the latest.
 
I wrote assembly code for the M files.

The M files are stored in a memory chip that interfaces to the SPIOGA ( special purpose input output gate array ) chip. The on board process and the PLC processor had to arbitrate to get access to the M files so access was not fast. Only one processor could access the M file at a time so the other processor had to wait while the other processor access the M file memory. There was a hand shaking mechanism for maintaining mutual exclusion.

I wouldn't call accessing the M files a block transfer but it was slow.

I wrote the code for the 1746-QS. I thought the SPIOGA chip was overly complicated for what it did. Other PLCs had much more efficient and probably much cheaper ways of accomplishing the same thing.

The 1746-QS and DeviceNet scanner used the SPIOGA chip. Someone at Rockwell had a sense of humor. The lettering on the SPIOGA chip said potato chip.
 
Just because the basic module isn't connected to anything doesn't mean its not doing something. It could be making large calculations or who knows. You need to trace the data going to/from it and see if the ladder program is using it for something. The good news is if it is doing something it should be easy enough to convert it to Logix 5000 Structured text or even ladder. Start by getting a Basic module manual and decipher the communications. You may get lucky and it may have been just printing alarms or data from the operation.
 

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