Super Systems AC20 RS485 Modbus - Manual (Page 15)

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TITLE: MODBUS/J-BUS Protocol for SSi’s- AC20 ENG. 824E REV. 1
N.B.:
Safety lock combination = 0: No security code (all parameters can always be
modified)
If safety lock combination is for control mode, ModBus
word 4002
÷
4011 are forced to 0.
Safety lock combination = 1: No security code (all parameters cannot be modified).
If safety lock combination is for control mode, ModBus
word 4002
÷
4011 are forced to 1.
Safety lock combination=2
÷
250: Security code for parameter protection.
In order to remove the protection for the control mode
parameters, it is necessary to write the safety lock
combination value for control mode at ModBus word
349. It is sufficient to do this once only.
In order to protect the control mode parameters, it is
necessary to write a value different from the safety
lock combination value for control mode at ModBus
word 349.
In order to modify the configuration parameters, it is
necessary to set the configuration mode by writing the
safety lock combination value for configuration mode
at ModBus word 347.
In order to modify the security code parameters, it is
necessary to set security code mode by writing the
safety lock combination value for configuration mode
at ModBus word 348.
ERROR REPLY
If the “error check” is wrong or the function code is not implemented or a buffer over flows
has been received, the slave does not send any reply to the master.
If other errors are detected in the request or command frame, or the slave cannot reply
with the requested values or it cannot accept the requested sets because it is in error
condition, the slave replies by forcing at “1” the bit 7 of the “Function code” byte followed
by an error code.
Error reply (from slave to master)
RANGE BYTE
Slave address 1
Function code (+80h) 1
Error code 1
Error check (CRC-16) 2