Memory Map; Memory Map Information; User Definable Memory Map Area - GE 469 Manual

6.4 MEMORY MAP

6.4 MEMORY MAP
The data stored in the 469 is grouped as Setpoints and Actual Values. Setpoints can be read and written by a
master computer. Actual Values are read only. All Setpoints and Actual Values are stored as two-byte values.
That is, each register address is the address of a two-byte value. Addresses are listed in hexadecimal. Data
values (setpoint ranges, increments, factory values) are in decimal.
Many Modbus communications drivers add 40001d to the actual address of the register addresses.
For example: if address 0h was to be read, 40001d would be the address required by the Modbus
communications driver; if address 320h (800d) was to be read, 40801d would be the address
NOTE
required by the Modbus communications driver.
The 469 has a powerful feature, called the User Definable Memory Map, which allows a computer to read up to
124 non-consecutive data registers (setpoints or actual values) by using one Modbus packet. It is often neces-
sary for a master computer to continuously poll various values in each of the connected slave relays. If these
values are scattered throughout the memory map, reading them would require numerous transmissions and
would burden the communication link. The User Definable Memory Map can be programmed to join any mem-
ory map address to one in the block of consecutive User Map locations, so that they can be accessed by read-
ing these consecutive locations.
The User Definable area has two sections:
1. A register index area (memory map addresses 0180h to 01FCh) that contains 125 actual values or set-
points register addresses.
2. A register area (memory map addresses 0100h to 017Ch) that contains the data at the addresses in the
register index.
Register data that is separated in the rest of the memory map may be remapped to adjacent register
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addresses in the User Definable Registers area. This is accomplished by writing to register addresses in the
User Definable Register Index area. This allows for improved through-put of data and can eliminate the need
for multiple read command sequences.
For example, if the values of Average Phase Current (register address 0306h) and Hottest Stator RTD Temper-
ature (register address 0320h) are required to be read from an 469, their addresses may be remapped as fol-
lows:
1. Write 0306h to address 0180h (User Definable Register Index 0000) using function code 06 or 16.
2. Write 0307h to address 0181h (User Definable Register Index 0001) using function code 06 or 16.
(Average Phase Current is a double register number)
3. Write 0320h to address 0182h (User Definable Register Index 0001) using function code 06 or 16.
A read (function code 03 or 04) of registers 0100h (User Definable Register 0000) and 0101h (User Definable
Register 0001) will return the Phase A Current and register 0102h (User Definable Register 0002) will return
Hottest Stator RTD Temperature.
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6.4.2 USER DEFINABLE MEMORY MAP AREA

469 Motor Management Relay
6 COMMUNICATIONS

6.4.1 MEMORY MAP INFORMATION

GE Power Management