B&B Electronics GW-7553 - Manual - Manual (Page 35)

GW-7553 PROFIBUS/Modbus TCP Gateway User Manual (Version 1.00, Dec/2008) PAGE: 35
“*” These error messages are not supported when the GW-7553 act as a Modbus
Slave.
PS:
Data Error：
a. GW-7553 acts as a Modbus Master
If the polling speed between the GW-7553 device and the Modbus Slave is
faster than the data exchange rate between PROFIBUS Master and the GW-
7553 then the PROFIBUS Master will not get all the data from the Modbus
Slave and therefore a diagnostic message (“PROFIBUS lose input data”) will be
send by the GW-7553 to the PROFIBUS Master
b. GW-7553 acts as a Modbus Slave
If the GW-7553 receives more telegram from the Modbus Master than it
transmits to the PROFIBUS Master then a diagnostic message (“PROFIBUS
lose input data”) will be send by the GW-7553 to the PROFIBUS Master.
c. When the GW-7553 receives a “data output command” (output byte 0) from
system setting module, and this command didn’t increase in order (ex: 0->1, 1-
>2,…, 255->0), the GW-7553 will think that it lose some output data of the
PROFIBUS Master and a diagnostic message (“Lose PROFIBUS output data”)
will be sent by the GW-7553 to the PROFIBUS Master.
4.6 I/O data exchange
The I/O data exchange is decided by Modbus type of the GW-7553 (please refer
section 4.3 The Configuration of the common parameters) between PROFIBUS
Master device and the GW-7553. Output data area of PROFIBUS Master device is
mapped into DO/AO memory of the GW-7553 and input data area of PROFIBUS
Master device is mapped into DI/AI memory of the GW-7553, when Modbus type
is Master. In the other way, Output data area of PROFIBUS Master device is
mapped into DI/AI memory of GW-7553 and input data area of PROFIBUS
Master device is mapped into DO/AO memory of GW-7553, when Modbus type
is Slave (please refer section 3.1 PROFIBUS data exchange ).
4.6.1 Input data area
The maximum length of input data is 128 bytes. Before arrange the input
module, the user must arrange and configure the system setting module. The
user can get data and control I/O of Modbus Slave device or get DI/DO/AI/AO
of the GW-7553 by read input module.