Delta Electronics Programmable Logic Controller DVP-PLC - Manual (Page 403)

8 Application Instructions API 100-149
DVP-PLC Application Manual 8-1
API Mnemonic Operands Function
100 MODRD Read Modbus Data
Controllers
ES/EX/SS SA/SX/SC EH/SV
Bit Devices Word Devices Program Steps Type
OP X Y M S K H KnX KnY KnM KnS T C D E F
S
1
* * *
S
2
* * *
n * * *
MODRD: 7 steps
PULSE 16-bit 32-bit
ES EX SS SA SX SC EH SV ES EX SS SA SX SC EH SV ES EX SS SA SX SC EH SV
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)