Download HA028014, Issue 4

COMMUNICATIONS MANUAL
CHAPTER 1 MODBUS GATEWAY FACILITY
This section describes the implementation of the Modbus Gateway facility as a part of a LIN instrument, in the
following subsections:
„
Overview of the Modbus Gateway Facility (Section 1.1)
„
Principles of operation (Section 1.2)
„
Using the diagnostic table (Section 1.3)
„
Modbus diagnostic function codes (Section 1.4)
„
Modbus exception responses (Section 1.5)
„
Notes on Modbus implementation (Section 1.6)
Note Some LIN products using a Modbus Gateway do not support Modbus Master mode.
1.1 OVERVIEW OF MODBUS GATEWAY FACILITY
The Modbus Gateway facility provides a Modbus interface to the LIN Database via the Serial or Modbus TCP
communications interface type on either a Modbus Master or Modbus Slave device. Only some LIN products support
Master mode, see appropriate instrument handbook.
Note A fault, e.g. cable is disconnected or device loses power, will cause a lose of communications between
the Master and Slave devices. Once the fault is fixed, Serial link communications can take up to
30 secs to be re-established. It can take up to 60 secs to re-establish Modbus TCP communications
By using the techniques of LIN function block caching, the Modbus Gateway facility can access data in other nodes
distributed on the LIN, as well as LIN function blocks in the local LIN Database.
Note Some instruments support more than a single Modbus Gateway facility.
„ Modbus - Serial
Master
The Serial communication interface type supports a
single Master device communicating to any number
of the Slave devices.
Slave
Slave
Slave
Figure 1.1a Serial communication interface type
„ Modbus - TCP
The Modbus TCP communication
interface type supports multiple
Master devices communicating to any
number of the Slave devices.
Master
Slave
Slave
Master
Slave
Master
Slave
Slave
Slave
Figure 1.1b TCP/IP communication interface type
HA028014
Issue 4 May 07
Chapter 1
Page 1 - 1