Fema B RTU Series, User Manual, Page: 14 / 36

FEMA ELECTRÓNICA . SERIES B . Models Bxx-RTU
14
1.19 Registers and functions : 32 bits ‘Process slave’
List of available registers (see Table 19) and available func -
tions
(see Table 20)
for instruments configured in ‘Process
slave’ mode and 32 bits data length.
• accessing a function not listed in the table, returns error
1 ‘Illegal Function’.
• accessing a register not listed in the table, returns error
2 ‘Illegal Data Address’.
• working with 16 bit registers allows for codification of
numbers between 32767 and -32767. If higher or lower
values are codified into a register, it will force the instru -
ment to overrange or underrange the reading.
• registers Setpoint 1, Setpoint 2 and Setpoint 3 are dis
-
abled by default (setpoint value is modified through the
front keypad). To enable access to read and write these
registers through the bus, while staying in ‘Process slave’
mode, see section 1.21.14.
- writing to the setpoint registers when they are disabled
returns error 2 ‘Illegal Data Address’.
- sending values higher than 999999 (or lower than
-199999) to the setpoint registers will save the value
999999 (or -199999)
- modifying a setpoint value manually from the front key
-
pad, does not update the value stored at the setpoint
register. Reading the setpoint register does not access the
setpoint value configured in the instrument, but the last
written value on the register.
• after power loss, the instrument starts up with all regis
-
ters initialized to ‘0’
(see section 1.16).
• registers of 32 bits are written with function ‘Write Mul -
tiple Registers’. Both registers (‘high’ and ‘low’) must be
written with the same write function. If write function is
received only for one of the registers (‘high’ or ‘low’) the
instrument will discard the write function. No error code
will be generated.
• the ‘Resolution’ register contains a numerical value indi
-
cating the number of decimal places on display. Valid val -
ues from 0 to 5. Writing value 2 lights the decimal point at
position XXXX.XX. Non valid values are discarded and no
error message is generated.
• all registers are read and write registers.
• access to reserved registers does not generate error
messages.
Example - to update the display of the instrument to a value
of 6543.21, it is needed to work with 32 bits registers. Con -
vert the value to hex format and write to the ‘Display high’
register the first 16 bits and to the ‘Display low’ register the
last 16 bits.
654321 decimal translated to hexadecimal is 0x0009FBF1
register ‘display high’ = 0x0009 = ‘9’
register ‘display low’ = 0xFBF1 = ‘64497’
When programming, this is directly achieved with functions
DIV (integer division) and MOD (rest of integer division).
register ‘display high’ = 654321 DIV 65536 = 9
register ‘display low’ = 654321 MOD 65536 = 64497
register ‘resolution high’ = 0
register ‘resolution low’ = 2
Register number Name
0 Display Low
1 Display High
2 Resolution Low
3 Resolution High
4 Setpoint 1 Low
5 Setpoint 1 High
6 Setpoint 2 Low
7 Setpoint 2 High
8 Setpoint 3 Low
9 Setpoint 3 High
10 Reserved
11 Reserved
Table 19 - Registers in 32 bits and ‘Process slave’ mode
Function number Name
16 Write multiple registers
3 Read registers
Table 20 - Functions in 32 bits and ‘Process slave’ mode