Some time ago, I posted a question asking about the Motorola SC44125P CPU, and I eventually determined that it is a custom 6800 with pre-programmed, dedicated data bus (8 bit) and address bus (16 bit) pins, along with the 6801 instruction set. Although it has the option, neither the on-board RAM or ROM are used.
After some brief comparison of later 68xx CPUs, I see the 68HC11 comes closest, but want to know which would be a suitable version (or newer replacement) that would work the best.
6801 or 68HC11 instruction set
Ability to disable on-board RAM / ROM
Dedicated 16-bit address bus pins or the ability to easily program same
Dedicated 8-bit data bus pins or ability to program same
Support pins required: R/~W, Clock input (1MHz), ~IRQ, ~IRQ2, ~NMI, and ~Reset
Sorry all the HC11 is obsoleted
So I can not recommend you any HC11 device.
If you want you can move to the S08 family like the mc9s08pb family
I hope this will help you