NEC 78K/0 Series - Manual (Page 17)

17
CHAPTER 2 REGISTERS
User's Manual U12326EJ4V0UM
2.2 General-Purpose Registers
General-purpose registers are mapped at particular addresses (FEE0H to FEFFH) of the data memory. These
registers consist of 4 banks, each bank consisting of eight 8-bit registers (X, A, C, B, E, D, L and H).
In addition that each register can be used as an 8-bit register, two 8-bit registers in pairs can be used as a 16-
bit register (AX, BC, DE and HL).
General-purpose registers can be described in terms of functional names (X, A, C, B, E, D, L, H, AX, BC, DE
and HL) and absolute names (R0 to R7 and RP0 to RP3).
Register banks to be used for instruction execution are set with the CPU control instruction (SEL RBn). Because
of the 4-register bank configuration, an efficient program can be created by switching between a register for normal
processing and a register for processing upon interrupt generation for each bank.
Table 2-1. General-Purpose Register Absolute Address Correspondence Table
Bank Name Register Absolute Address Bank Name Register Absolute Address
Functional Absolute Functional Absolute
Name Name Name Name
BANK0 H R7 FEFFH BANK2 H R7 FEEFH
L R6 FEFEH L R6 FEEEH
D R5 FEFDH D R5 FEEDH
E R4 FEFCH E R4 FEECH
B R3 FEFBH B R3 FEEBH
C R2 FEFAH C R2 FEEAH
A R1 FEF9H A R1 FEE9H
X R0 FEF8H X R0 FEE8H
BANK1 H R7 FEF7H BANK3 H R7 FEE7H
L R6 FEF6H L R6 FEE6H
D R5 FEF5H D R5 FEE5H
E R4 FEF4H E R4 FEE4H
B R3 FEF3H B R3 FEE3H
C R2 FEF2H C R2 FEE2H
A R1 FEF1H A R1 FEE1H
X R0 FEF0H X R0 FEE0H