8 Application Instructions API 100-149 API 100 Operands: S 1 : Address of communication device S 2 : Address of data to be read n : Length of read data Explanations: 1. Range of S 1 : K0 ~ K254 2. Range of n : K1 ≤ n ≤ K6 3. See the specifications of each model for their range of use. 4. ES/EX/SS series MPU does not support E, F index register modification. 5. Flags: See API 80 RS for explanations on M1120 ~ M1131, M1140 ~ M1143 6. MODRD is a drive instruction exclusively for peripheral communication equipment in MODBUS ASCII mode /RTU mode. The built-in RS-485 communication ports in Delta VFD drives (except for VFD-A series) are all compatible with MODBUS communication format.
MODRD can be used for controlling communication (read data) of Delta drives. 7. If the address of S 2 is illegal to the designed communication device, the device will respond with an error, PLC will records the error code in D1130 and M1141 will be On. 8. The feedback (returned) data from the peripheral equipment will be stored in D1070 ~ D1085. After receiving the feedback data is completed, PLC will auto-check if all data are correct. If there is an error, M1140 will be On. 9. In ASCII mode, due to that the feedback data are all in ASCII, PLC will convert the feedback data into numerals and store them in D1050 ~ D1055. D1050 ~ D1055 will be invalid in RTU mode. 10.
After M1140 or M1141 turn On, the program will send a correct datum to the peripheral equipment. If the feedback datum is correct, M1140 and M1141 will be reset. Program Example 1: Communication between PLC and VFD-S series AC motor drives (ASCII Mode, M1143 = Off) MOV M1002 Set up communication protocol 9600, 8, E, 1 SET M1120 Retain communication protocol X1 MOV Set up communication time-out: 100ms SET M1122 Set up sending request DVP-PLC Application Manual 8-1 Mnemonic Operands Function MODRD Read Modbus Data Type OP Bit Devices Word Devices Program Steps X Y M S K H KnX KnY KnM KnS T C D E F MODRD:
7 steps S 1 * * * S 2 * * * n * * * PULSE 16-bit 32-bit SS SA SX SC EH SV EH3 SV2 EH3 ES EX SS SA SX SC EH SV EH3 SV2 ES EX ES EX SS SA SX SC EH SV SV2 H87 D1120 K100 D1129