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+--- Thread: Modbus - Write bits in word (/showthread.php?tid=1777)
Modbus - Write bits in word - JohnTH - 07.12.2018
Hi,
I have to write bits in a 16-bit register (bitmask) see attachment. This is a control-word for a eaton DC1 freq.converter.
On start I have to set
Bit2=Fault reset, and Bit8=Control
Speed reference is set to another register.
I found this thread about reading bit in a bitmask, but can`t figure out how to use the function to write.
https://forum.logicmachine.net/showthread.php?tid=522&pid=2850#pid2850
-John
RE: Modbus - Write bits in word - admin - 07.12.2018
This script will set bit 0 if 1/1/1 is on, bit 1 if 1/1/2 is on etc. Adjust as needed and add writing to ModBus register at the end of the script.
Code:
function setbit(value, bitnr)
local mask = bit.lshift(1, bitnr)
return bit.bor(value, mask)
end
value = 0
if grp.getvalue('1/1/1') then
value = setbit(value, 0)
end
if grp.getvalue('1/1/2') then
value = setbit(value, 1)
end
if grp.getvalue('1/1/3') then
value = setbit(value, 2)
end
log(value)RE: Modbus - Write bits in word - JohnTH - 07.12.2018
Thank you!
RE: Modbus - Write bits in word - iJAF - 12.03.2019
Hello,
I have also made the inverse resetbit() function that could be useful :
Code:
function resetbit(value, bitnr)
local mask
mask = bit.lshift(1, bitnr)
mask = bit.bnot(mask)
return bit.band(value, mask)
end