Grossel
Well-Known Member
Hi.
I'm asking here because Google cannot provide an answer on this.
I know a modbus master device are polling each slave device in order for the slave device to either read or write some data. And I know each slave can have many registers to read or write data to.
But what I don't know is if the modbus master is polling each register in each slave per poll, or does it retrieve/send all possible (or possible filtered) data that each modbus slave possible can hold in one big data package?
Example: Say a slave device has 100 different registers. Does the modbus master then poll 100 times against that slave device, one poll for each register?
Or does the modbus master poll one time to the modbus slave and then write to any or all registers and read all registers in one chunk?
Or is it somewhere between ?
That is probably a stupid question, and not relevant in order to get two devices to talk to each other - but I want to drill into this, and it's just frustrating that I cannot find any sources mention this. I feel it's like learning to drive a car, but never actually being able to see the car from outside so you don't know anything about tires nor steering and propulsion concepts.
I'm asking here because Google cannot provide an answer on this.
I know a modbus master device are polling each slave device in order for the slave device to either read or write some data. And I know each slave can have many registers to read or write data to.
But what I don't know is if the modbus master is polling each register in each slave per poll, or does it retrieve/send all possible (or possible filtered) data that each modbus slave possible can hold in one big data package?
Example: Say a slave device has 100 different registers. Does the modbus master then poll 100 times against that slave device, one poll for each register?
Or does the modbus master poll one time to the modbus slave and then write to any or all registers and read all registers in one chunk?
Or is it somewhere between ?
That is probably a stupid question, and not relevant in order to get two devices to talk to each other - but I want to drill into this, and it's just frustrating that I cannot find any sources mention this. I feel it's like learning to drive a car, but never actually being able to see the car from outside so you don't know anything about tires nor steering and propulsion concepts.