Toshiba G7 - Manual (Page 45)

G7 ASD Multi-Protocol Communication Option and PG Feedback Option Manual 38
10.2.3 Modbus/ASD Register Mappings
The Multicom Modbus interface acts as a relatively straightforward network gateway for the ASD into
which it is installed. In general, Modbus holding registers (4X references) are directly mapped to
corresponding ASD registers (also sometimes referred to as “communication numbers” or “parameter
numbers”) with a direct 1-to-1 correspondence. The relationship between Modbus holding registers and
their ASD register counterparts is as follows:
Modbus holding register = ASD register + 1
This means that in order to access a specific ASD register, simply add 1 to its index and access that
Modbus holding register. The reason for this offset is due to the fact that ASD registers begin at index
0, while Modbus holding registers begin at index 1.
The only minor exception to the above 1-to-1 mapping takes place in the “upper address” registers in the
ASD. By inspecting the
Toshiba Serial Communications Manual, one can observe that the ASD
registers are divided into two distinct regions within the full 0x0000 ~ 0xFFFF ASD register map: the
“lower address” range covers from 0x0000 to 0x09FF, and the “upper address” range covers from
0xFA00 to 0xFFFF (not all values within those ranges access valid ASD registers, of course). For
access consistency and because some Modbus clients are unable to access holding registers with indexes
greater than 9999
10
(0x270F), the Multicom Modbus interface automatically maps all “upper address”
ASD registers into the contiguous region immediately following the “lower address” range. To take
advantage of this feature, simply drop the initial “F” on any register index in the “upper address” range
(and add 1 to that number to obtain the corresponding Modbus register), and the register request will
automatically access the correct internal ASD register.
For example, if we wish to read ASD register 0xFE06 (input terminal status), we would change the
0xFE06 to 0x0E06, and then add 1 to obtain the resultant Modbus register: 0x0E07 (3591
10
).
Therefore, making a request to read Modbus register 0x0E07 will return the input terminal status located
at ASD register 0xFE06. If desired, it is also acceptable to access the “upper address” registers at their
original locations, as their default (0xFXXX) locations can still be accessed. Continuing with the
previous example, ASD register 0xFE06 can therefore be equally accessed by requesting either Modbus
register 0x0E07 or 0xFE07 (65031
10
).
In order to avoid any possible confusion regarding this register-mapping scheme, this manual will
always explicitly use the terms “ASD register” or “Modbus register” where the intended usage may not
be clear. If the term “register” is used alone, then “Modbus register” will be the intended meaning by
default.
With the exception of the “upper address” register mapping feature explained above and the
programmable pointer registers feature detailed in Section 10.2.6, the Multicom Modbus interface does
not in any way modify or otherwise alter valid register access requests originating from the Modbus
client. By adhering to this design parameter, the availability and interpretation of any Modbus registers
is entirely determined by the attached drive. In this way, the Modbus interface allows itself to become
virtually “transparent” on the network, essentially allowing the Modbus client to carry on a dialog
directly with the drive.
An overview of the entire mapping configuration can be found in Section 10.2.9.