Fault Records; Figure 5-38. Function 23 Read/Write Command Format - ABB TPU2000 Technical Manual

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The command response is generated to the Host from the TPU2000/2000R after the action is completed.
The defined control blocks 1 and 2 are write capable and are well suited for access control via the Modbus
command 16 (10 HEX).
Function 23 Read/Write Register (Read/Write Concurrently)
Another format command which allows for a simultaneous read/write is command 23 (17HEX). Figure 5-38
illustrates the Read/Write 4X Register command format. The 23 command is used when the user wishes to write
a register for control buffer access and read a group of registers which was accessed via the read.
Control Blocks 1 and 2 allows for access of protective device function state. If a user wished to read the status of
each function within the relay, a Function Read/Write Register Command would be the most desirable command
to be issued. Read/Write register data commands are also useful in accessing the Operation, Differential Fault,
Through Fault and Harmonic Restraint Fault record blocks.
Review of the Modbus 23 command allows for write and read of data if the total amount of read and write
registers do not exceed over 125 words. An advantage of using a combined read/write command is that of
speed. If conventional commands were to be used, a 16 Write 4X Register Command would be issued and
thereafter, within 10 seconds, a 03 Modbus (Read 4X Register Command) would then be issued to extract the
data from the relay. Using Modbus command 23 allows for decreasing of the overhead associated with multiple
register reads and writes.

Fault Records

Fault records are stored in the TPU2000/2000R according to the following format. Figure 5-39 illustrates the
method of accessing the Fault Record Data via the TPU2000/2000R. The TPU2000/2000R has an internal
circular buffer, which stores a maximum of 32 faults. These faults are stored internally to the TPU2000/2000R's
fault stack as indicated in the figure. Each fault is defined as a block of registers. The first defined register in the
table is the fault record control register. Fault records are viewed by writing a data word to the first register in the
data stack as defined for each Fault Record stack and reading the block of consecutive registers for that stack.
Table 5-32 lists the type of Fault Record available in the TPU2000R, the Modbus Control Register Address and
the Data Stack Address to retrieve the fault information.
TPU2000/2000R Modbus/Modbus Plus Automation Guide
Function 23 Read/Write 4X Registers
S Slave Funct. Read Read #Regs
Addr. Code Addr Addr Read
O
17 HI LO HI
M
Byte 1 ...2........3.......4.......5......6........7.... ..8.........9.....10......11......12...........X
Command
Allows 125 Regs.
Max.
Slave
SOM Addr.
SOM = Start of Message
EOM = End of Message
MSB
Register Hi Byte
151413121110 9 8

Figure 5-38. Function 23 Read/Write Command Format

#Regs #Regs Byte
Write
#Regs Write
Writ. Writ. Count
Addr
Read Addr
HI LO
LO HI LO
Modbus Host
Funct. Byte Data Data
Code Count Byte Byte
17 * Hi Lo
MSB
LSB
LSB
7 6 5 4 3 2 1 0
Data Data E
Error
Check O
*
HI LO
M
Modbus Slave Addr =1
E C
Data
Error
EOM
Byte
Check
Lo
115