3 . I ns t r uc ti on Se t3- 2 8 1API Mnemonic Operands Function ControllersES2/EX2 SS2 SA2SESX2100 MODRD Read Modbus DataTypeOPBit Devices Word devices Program StepsX Y M S K H KnX KnY KnM KnS T C D E F MODRD: 7 stepsS1 * * *S2 * * *n * * *PULSE 16-bit 32-bitES2/EX2 SS2 SA2SE SX2 ES2/EX2 SS2 SA2SE SX2 ES2/EX2 SS2 SA2SE SX2Operands:S1: Device address (K0~K254) S2: Data address n: Data length (K1＜n≦K6)Explanations:1. MODRD instruction supports COM2 (RS-485).2. MODRD is an instruction exclusively for peripheral communication equipment in MODBUSASCII/RTU mode. The built-in RS-485 communication ports in Delta VFD drives (except forVFD-A series) are all compatible with MODBUS communication format. MODRD can be usedfor communication (read data) of Delta drives.3. If the address of S 2 is illegal for the designated communication device, the device will respondwith an error, PLC will record the error code in D1130 and M1141 will be ON.4. The feedback (returned) data from the peripheral equipment will be stored in D1070 ~ D1085.After data receiving is completed, PLC will check the validity of the data automatically. If there isan error, M1140 will be ON.5. The feedback data are all ASCII codes in ASCII mode, so PLC will convert the feedback datainto hex data and store them in D1050 ~ D1055. D1050 ~ D1055 is invalid in RTU mode.6. If peripheral device receives a correct record (data) from PLC after M1140/M1141 = ON, theperipheral device will send out feedback data and PLC will reset M1140/M1141 after the validityof data is confirmed.7. There is no limitation on the times of using this instruction, but only one instruction can beexecuted at a time on the same COM port.8. Rising-edge contact (LDP, ANDP, ORP) and falling-edge contact (LDF, ANDF, ORF) can not beused with MODRD instruction, otherwise the data stored in the receiving registers will beincorrect.9. For associated flags and special registers, please refer to Points to note of API 80 RSinstruction.
