NEC PD754144 - Manual (Page 34)

CHAPTER 3 FEATURES OF ARCHITECTURE AND MEMORY MAP
34 User’s Manual U10676EJ3V0UM
3.1.2 Addressing mode of data memory
The 75XL architecture employed for the µPD754244 provides the seven types of addressing modes shown in Table
3-1. This means that the data memory space can be efficiently addressed by the bit length of the data to be processed
and that programming can be carried out efficiently.
(1) 1-bit direct addressing (mem.bit)
This mode is used to directly address each bit of the entire data memory space by using the operand of an
instruction.
The memory bank (MB) to be specified is fixed to 0 in the mode of MBE = 0 if the address specified by the
operand ranges from 00H to 7FH, and to 15 if the address specified by the operand is 80H to FFH. In the
mode of MBE = 0, therefore, both the data area of addresses 000H to 07FH and the peripheral hardware area
of F80H to FFFH can be addressed.
In the mode of MBE = 1, MB = MBS; therefore, the entire data memory space can be addressed.
This addressing mode can be used with four instructions: the bit set and reset instructions (SET1 and CLR1),
and the two bit test (SKT and SKF).
Example To set FLAG1, reset FLAG2, and test whether FLAG3 is 0
FLAG1 EQU 03FH.1 ; Bit 1 of address 3FH
FLAG2 EQU 057H.2 ; Bit 2 of address 57H
FLAG3 EQU 077H.0 ; Bit 0 of address 77H
SET1 MBE ; MBE
← 1
SEL MB0 ; MBS
← 0
SET1 FLAG1 ; FLAG1 ← 1
CLR1 FLAG2 ; FLAG2 ← 0
SKF FLAG3 ; FLAG3 = 0?