RS485 connection with PM-902F.
Please help me with RS-485 connection with AC-900F controller.
Redundant Controller, configuring Controller as Modbus master and using MODM_R8R block to read data.
Actually i want to take data of energy meter on modbus. I am connecting postive, negative cable from meter to 2,3 port of serial interface- 1 of primary controller, but not able to get the data.
While, able to get data on modscan when connecting through rs485-rs232 converter.
PLease let me know if i am doing something not appropriate.
The serial interface in AC900F controller can be configured as RS232 or RS485. (ensure you have selected the correct mode in MODM_DEV)
Second point is, for RS485, you need to electrically close every bus segment using 120ohm resistor. Please refer M&I instructions for more details.
Start with minimum configuration:
1. Single controller
2. HW AC900F P must be connected with + or B on meter, and AC900F N with – or A on mete (plus with plus/minus with minus)
3. You need to insert the internal pull-up resistor by a short wire link between terminal 1 and 2, and insert the internal pull-down resistor by a short wire link between the terminal 3 and 4.
Insert terminal resistor 2-3 (only on the end of line, not on both AC900F)
Page 80 and 81 of the M&I AC900F Controller manual
4. Check correct baud rate, number of bits, parity and stop bit for Master and slave
5. Check slave address setting on both sides
6. Test with function code 8 diagnostic, meter might not support this function code.
7. Create TEST SW with minimum configuration use only one MODM_R8R with one word and one variable connected on R1.
8. Check MODM_R8R STA pin for diagnostic, check manual for diagnostic
Set MODM_R8R start address (check meter configuration for values) often address 4001 or 40001 could be start address 0 or 1 in MODM_R8R.