A device at a unit address, 1 to 247, with every table empty. Throws for 0, the broadcast address, and for 248 to 255, which the specification reserves.
How many requests the device has carried out, broadcasts included and refusals not.
The device's unit address.
Answers one RTU frame, as the device on the line does, or returns null when it stays
silent.
A coil's state, or null when the device has no coil there.
A discrete input's state, or null when the device has no input there.
A holding register's value, or null when the device has no register there.
An input register's value, or null when the device has no register there.
Sets coils from an address on, adding any the device did not have.
Sets discrete inputs from an address on, adding any the device did not have.
Sets holding registers from an address on, adding any the device did not have.
Sets input registers from an address on, adding any the device did not have.
A Modbus device: a unit address and the four tables it serves, coils, discrete inputs, holding registers, and input registers, each holding only the addresses it was given.
answertakes one RTU frame and returns the frame the device sends back, ornullwhen it stays silent: the frame failed its CRC, is for another unit, or is a broadcast, whose write the device still carries out. A request it cannot serve is answered with the exception the specification gives.