link says that the Z800 was the NMOS version of what later became the CMOS Z280. link says that the R800 was based on the Z800 with the same instruction set. link lists the R800 instruction set, and it is exactly the same as the Z80, with the addition of the Z280's MULT A,r and MULT HL,rr instructions.

R800 additional opcodes over Z80:

ED C1 MULTU A,B            ED C3 MULTU HL,BC
ED C9 MULTU A,C
ED D1 MULTU A,D            ED D3 MULTU HL,DE
ED D9 MULTU A,E
ED E1 MULTU A,H            ED E3 MULTU HL,HL
ED E9 MULTU A,L
ED D1 MULTU A,(HL)         ED F3 MULTU HL,SP
ED D9 MULTU A,A