how to use M66 as code

Firstly, you can't do an analogue output from the parallel port. (You probably know this, but I thought it worth saying).

The M66 etc analogue/digital inputs/outputs are from G-code to HAL.
Stepconf will allow you to set a parallel port pin to be digital_out 0 to 3 if it is an output pin, or a digital input for an input pin.

It might be worth setting up a pin as a digital in or out to see what that looks like in the HAL file.

It creates a link in HAL between the pin motion.digital-out-n to the selected p-port pin.
Typically the analogue inputs and outputs from G-code never escape the software layers, being linked to user-interface elements. However there is no reason that you couldn't connect in HAL to the command value of a PWM generator, or the read value of an encoder velocity.

It might help to tell use what you want to do, rather than ask for help with your specific solution.

shine wrote:

andypugh

I might understand what you mean.

for using analog output and input, we must use DAC( digital to analog converter) to parallel port on the circuit.

Indeed. Digital-to-analog is relatively easy using a PWM component and then a hardware filter (resistor and capacitor) to convert to a voltage.
Analogue input is rather more difficult. It is generally easier to use a voltage-to-frequency device and measure the frequency using the HAL encoder function.

Alternatively, there are non-parallel-port solutions.