The buttons are accessed same ways as for Digital Joysticks (ie. as part of the keyboard matrix).
The analog inputs are read from memory mapped ASIC registers:
6808h ADC0 Analogue Joystick 1, X-Axis (00h=Left= [maybe 0 ohm???], 3Fh=Right= [maybe 1xx Kohm???])
6809h ADC1 Analogue Joystick 1, Y-Axis (00h=Up= [maybe 0 ohm???], 3Fh=Down = [maybe 1xx Kohm???])
680Ah ADC2 --unknown: MIGHT be Analogue Joystick 2, X-Axis (or Y-Axis, or whatever)
680Bh ADC3 --unknown: MIGHT be Analogue Joystick 2, Y-Axis (or X-Axis, or whatever)
680Ch ADC4 --unknown: MIGHT be unused (maybe wired to GND or VCC)
680Dh ADC5 --unknown: MIGHT be unused (maybe wired to GND or VCC)
680Eh ADC6 --unknown: MIGHT be unused (maybe wired to GND or VCC)
680Fh ADC7 --unknown: MIGHT be unused (maybe wired to GND or VCC)
To read that registers: Unlock the ASIC, and then map its register to memory at 4000h..7FFFh.
== Analog CPC+ Joysticks ==