1X Discrete Contact Inputs; Function Code 2 - Read Input Status (Read Only Data) - ABB TPU2000 Technical Manual

Discrete Item
Address
01048 OUT 4
01049 OUT 3
01050 OUT 3
01051 OUT 2
01052 OUT 2
01053 OUT 1
01054 OUT 1
01055 TRIP Status
01056 TRIP Momentary

1X Discrete Contact Inputs

Discrete physical input and relay element status are available via a function 02 request through Modbus and
through a Modbus Plus Host. The TPU2000/2000R does not support the Modbus Plus feature of PEER COP
thus 1X data cannot be obtained from a PLC (Programmable Logic Controller) supporting such a feature. Figure
5-19 illustrates a typical command sequence. The Host polls the TPU2000R for the Data. The TPU2000R
receives the request and responds with the expected data. The Host then interprets the command response,
checks the LRC checksum in ASCII mode and then displays the interpreted data. If the node is configured for
RTU Modbus, the start of message character is three character delays, and the end of message consists of a
CRC-16 checksum and three character delays. Additional information is available in Modicon's protocol manual
references listed at the beginning of this document. The same information is available through a 4X register read
command, which allows a host without 1X data accesses capabilities to obtain physical input and relay element
information. Tables 5-5 through 5-9 list the 1X discrete contact memory map as defined for Modbus RTU and
ASCII. Modbus Plus embeds the Modbus message in its structure. Please reference Section 5 of this document
for a more complete discussion of Modbus Plus message structure.

Function Code 2 - Read Input Status (Read Only Data)

Figure 5-19 illustrates the command format required for execution of function code 2.
SOM
SOM = Start of
EOM = End of
Figure 5-19. 1X Input Request Using Modbus Command 02
It should be noted that every TPU2000R allows real time status reporting when the unit is polled. If a status is
momentary and is missed during the host poll, then the data is lost. Polling using the status Momentary Change
Detect Feature insures that the host device does not miss the momentary change. It should also be noted that
data requested from 1X data address ranges not defined within this document generates Modbus exception
codes.
TPU2000/2000R Modbus/Modbus Plus Automation Guide
Physical Output Contact 4 Change Detect Between Scans
Physical Output Contact 3
Physical Output Contact 3 Change Detect Between Scans
Physical Output Contact 2
Physical Output Contact 2 Change Detect Between Scans
Physical Output Contact 1
Physical Output Contact 1 Change Detect Between Scans
Breaker Trip Physical Output Contact
Breaker Trip Physical Output Contact Change Detect Between Scans
Slave Funct. Start Start Coils
Addr. Code Addr Addr Read
02 HI LO
Byte 1 ...2........3.......4.......5......6........7....
Modbus Host
SOM
Message Header
Message Header
MSB
Description
Coils Error
EOM
Read Check
HI LO
Slave Funct. Byte Data
Addr. Code Count Byte
02 * 1
LSB
8 7 6 5 4 3 2 1
Modbus Slave Addr =1
E C
Read from
1X Mapping
Data Error
EOM
..... Byte Check
NNN
63