Multilin SR469 Instruction Manual Download

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6. COMMUNICATIONS

MEMORY MAP

6-15

6.5 MEMORY MAP

6.5.1

MEMORY MAP

INFORMATION

The data stored in the SR469 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 ad-
dress of a two byte value. Addresses are listed in hexadecimal. Data values (Setpoint ranges, increments, factory values) are in deci-
mal.

Note: Many Modbus communications drivers add 40001d to the actual address of the register addresses. For example: if ad-
dress 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 required by the Modbus communications driver.

6.5.2

USER DEFINABLE MEMORY MAP AREA

The SR469 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 necessary 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
memory map address to one in the block of consecutive User Map locations, so that they can be accessed by reading these consecutive
locations.

The User Definable area has two sections:

1. A Register Index area (memory map addresses 0180h-01FCh) that contains 125 Actual Values or Setpoints register addresses.
2. A Register area (memory map addresses 0100h-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 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 im-
proved 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 Temperature (register address
0320h) are required to be read from an SR469, their addresses may be remapped as follows:

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.

6.5.3

EVENT RECORDER

The SR469 event recorder data starts at address 3000h. Address 3003h is a pointer to the event of interest (1 representing the latest
event and 40 representing the oldest event). To retrieve event 1, write ‘1’ to the Event Record Selector (3003h) and read the data from
3004h to 3022h. To retrieve event 2, write ‘2’ to the Event Record Selector (3003h) and read the data from 3004h to 3022h. All 40
events may be retrieved in this manner. The time and date stamp of each event may be used to ensure that all events have been re-
trieved in order without new events corrupting the sequence of events (event 1 should be more recent than event 2, event 2 should be
more recent than event 3, etc...).