Teco Westinghouse A510 VFD comms

[wolf3000]

Hello:
I am confused about the A510 modbus addressing scheme. According to Teco's communication addendum the modbuss register addresses start at 2500H which is equivalent to 9472 dec. I have never seen this before. I was under the impression that modbus holding register addresses started at 4000. Can someone enlighten me as to how the Teco addresses work?

 

[cottagewood]

Add a 4 to the front 49472

 

[bigmuz]

Is this for rtu ascii addressing? If I am using hex addressing and I want to read 2533H do I use the RTU Hex driver and 2533 is the address? 3x is read the register?

Thank you

 

[danw]

Modbus addresses start wherever the device manufacturer says they start. There is nothing that says that any vendor's mapp has to start with Holding Register (4)0001 (there's never a (4)0000 in one-based addressing). I've seen lots of devices with register maps that do not start at the 'low end' of the memory area addressing.

comm manual here:
https://www.tecowestinghouse.com/PDF/A510_comm_addendum.pdf

page 1-2
"Function Code 03H: read the register contents"

That tells me that the registers listed are Holding registers (not Input registers) which are read by Function code 0x03

Register 0x2500 is hex and hex addresses are always zero-based address numbering (numbering starts at zero, not one).

Many, many master use "memory area" addressing which uses a leading numeral in front of the indexed register value to indicate what type of register it is. The numeral (4) is always used to indicate Holding Registers. Memory area addressing is one-based, where the first register (whether it is used or not) is one, which for Holding Registers is (4)0001 or (4)00001. Problem is, sometimes the master data entry 'assumes' the (4)xxxx format and the user enters only the indexed value, not the leading numeral (4).

For any hex register in the table, add 40001 to the decimal equivalent to get the memory area based, onebased register value.

0x2506 (Analog output value) = decimal 9478 (zero based), which equates to (4)9479 (5 digit addressing) or (4)09479 (6 digit addressing)

 

[bigmuz]

Thanks my man, that is super generous of you to respond in great detail.

I moved to the weintek zero based addressing modbus driver and I at least have comms established. I will bash my way through it and figure it out now.

Many thanks!