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Introduction to the RC800 family
The RC800 family is an experiment that explores what a hypothetical 8 bit CPU introduced in the mid to late 1980's might look like, if certain dogmas such as FWIW and RISC techniques had been applied.
It is inspired by several existing architectures, such as the Z80, MIPS, and 68000. The ISA has been designed so it will fit into a four stage RISC pipeline.
Internally it has eight 8 bit registers. These are named F (for Flag), T (Temporary), B, C, D, E, H, and L. They can also be combined to form four 16 bit registers - FT, BC, DE, and HL. There's an extensive set of instructions that perform 16 bit operations, such as comparisons, shifts and addition. There's also a program counter, interrupt enable flag, stack pointers and a set of configuration registers.
The architecture features on-chip stacks, one per each register pair. All registers can be pushed at once, enabling very fast interrupt response.
The first implementation is called RC811.