Performance Tips - Toshiba VF-A7 Instruction Manual

10.8 Performance Tips

This section offers several configuration tips which can help to optimize the
performance of communications with the ETH-100 and attached drives.
1. Configure Modbus programmable pointer registers to also be drive scan
registers. In the example configuration shown in Table 3, Modbus registers
FC00 ~ FC07 are configured to point to the ASD scan registers. In this case, a
Modbus transaction beginning at address FC00 with a length of 8 can be
processed extremely fast. Of course, pointer registers can still be accessed if
they are not configured as scan registers, but the transactions are slower, as they
require transferring the request to the drive for processing.
ASD Scan Registers
Register
FA01
FA00
FD00
FE01
FC90
FE03
FE42
FA22
2. Don't leave a gap in the access sequence. For optimal network response,
make sure all of the pointer registers that you are going to access are also
configured to be ASD scan registers. The ETH-100 is most effective when all of
the pointer registers that are going to be accessed are also ASD scan registers.
In the example shown in Table 4, the high-speed processing of a Modbus register
read starting at register 0xFC00 with a length of 8 will be delayed by the necessity
to interact with the drive to obtain the values of drive registers 0xFC90 and
0xFE03.
ASD Scan Registers
Register
FA01
FA00
FD00
FE01
FE42
FA22
Table 3: Efficient Scan/PPR Configuration
R/W Value
Read
Read
Read
Read
Read
Read
Read
Read
Table 4: Inefficient Scan/PPR Configuration
R/W Value
Read
Read
Read
Read
Read
Read
Modbus Pointer Registers
Register
FC00
FC01
FC02
FC03
FC04
FC05
FC06
FC07
Modbus Pointer Registers
Register
FC00
FC01
FC02
FC03
FC04
FC05
FC06
FC07
32
Points To...
FA02
FA01
FD01
FE02
FC91
FE04
FE43
FA23
Points To...
FA02
FA01
FD01
FE02
FC91
FE04
FE43
FA23