NEC PD78056F, User Manual

Page: 106 / 593

106
CHAPTER 5 CPU ARCHITECTURE
5.2.2 General registers
A general register is mapped at particular addresses (FEE0H to FEFFH) of the data memory. It consists of 4 banks,
each bank consisting of eight 8-bit registers (X, A, C, B, E, D, L and H).
Each register can also be used as an 8-bit register. Two 8-bit registers can be used in pairs as a 16-bit register
(AX, BC, DE and HL).
They can be described in terms of function 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 interruption for each bank.
Table 5-2. Corresponding Table of General Register Absolute Address
Register Register
Function Absolute Function Absolute
Name Name Name Name
BANK0 H R7 F E F F H BANK2 H R7 F E E F H
L R6 F E E E H L R6 F E E E H
D R5 F E E D H D R5 F E E D H
E R4 F E F C H E R4 F E E C H
B R3 F E F B H B R3 F E E B H
C R2 F E F A H C R2 F E E A H
A R1 F E F 9 H A R1 F E E 9 H
X R0 F E F 8 H X R0 F E E 8 H
BANK1 H R7 F E F 7 H BANK3 H R7 F E E 7 H
L R6 F E F 6 H L R6 F E E 6 H
D R5 F E F 5 H D R5 F E E 5 H
E R4 F E F 4 H E R4 F E E 4 H
B R3 F E F 3 H B R3 F E E 3 H
C R2 F E F 2 H C R2 F E E 2 H
A R1 F E F 1 H A R1 F E E 1 H
X R0 F E F 0 H X R0 F E E 0 H
Bank Name Absolute Address Bank Name Absolute Address