User manual

ManualsBrandsBaldor ManualsComputer equipmentModbus Plus

2 Modbus RTU MN744

Application Layer Specification

The host (master) communicates with the H2 drive (the slave) using a predefined list of standard Modbus

functions codes. Table 1 summarizes these function codes.

Table 1 Standard Function Code Implementation

H2 Reference Sets Modbus Standard Function Codes

Control Bits

Relay Outputs

Coils (0xxxx) 01 - Read coil Status

15 - Write multiple coils

Status Bits

Discrete Inputs

Discrete Inputs (1xxxx) 02 - Read input discrete

Analog Inputs Input Registers (3xxxx) 04 - Read input register

Control Words

Status Words

References

Parameters

Holding Registers (4xxxx) 03 - Read multiple registers

16 - Write multiple registers

Poll Controller None 14 - Poll slave after master receives an ACK (05) from a slave to

complete the transaction

Data Acquisition None 68 - Special function used obtaining debug data from H2.

S Read Internal Value (internal use only)

S Write Internal Value (internal use only)

S Configure O-Scope

S Control O-Scope

S Acquire O-Scope Data

S Read Active Fault Codes

Drive Enumeration None 69 - Workbench connect and enumeration

S To Be Determined

Table 2 Data Types

Keyword Size Bytes Description Minimum Maximum

INT32 4 Double Integer -2

-1

UINT32 4 Unsigned double integer 0 2

-1

FLOAT32 4 IEEE floating point std. 754 (single precision) ±1.175 x10

±3.403 x10

Table 3 MODBUS Exception Codes

Code Name Description

01 ILLEGAL FUNCTION The function code received in the query is not an allowable action for the server (or slave). This may be because the

function code is only applicable to newer devices, and was not implemented in the unit selected. It could also indicate

that the server (or slave) is in the wrong state to process a request of this type, for example because it is un-configured

and is being asked to return register values.

02 ILLEGAL DATA ADDRESS The data address received in the query is not an allowable address for the server (or slave). More specifically, the

combination of reference number and transfer length is invalid. For a controller with 100 registers, a request with offset

96 and length 4 would succeed, a request with offset 96 and length 5 will generate exception 02.

03 ILLEGAL DATA VALUE A value contained in the query data field is not an allowable value for server (or slave). This indicates a fault in the

structure of the remainder of a complex request, such as that the implied length is incorrect. It specifically does NOT

mean that a data item submitted for storage in a register has a value outside the expectation of the application program,

since the MODBUS protocol is unaware of the significance of any particular value of any particular register.

04 SLAVE DEVICE FAILURE An unrecoverable error occurred while the server (or slave) was attempting to perform the requested action.

05 ACKNOWLEDGE Specialized use in conjunction with programming commands. The server (or slave) has accepted the request and is

processing it, but a long duration of time will be required to do so. This response is returned to prevent a timeout error

from occurring in the client (or master). The client (or master) can next issue a Poll Program Complete message to

determine if processing is completed.

06 SLAVE DEVICE BUSY Specialized use in conjunction with programming commands. The server (or slave) is engaged in processing a long duration

program command. The client (or master) should retransmit the message later when the server (or slave) is free.