NEC PD75402A User Manual page 45

(2) Peripheral hardware area
The peripheral hardware area is mapped to memory bank 15's addresses F80H to FFFH.
The operation is performed by the memory manipulation instruction just as in the static RAM. In the peripheral
hardware, however, the operable bit unit differs from one address to another. It is impossible to access an address
to which the peripheral hardware is not assigned since the data memory is not built in. (See Table 3-4 " PD75402A
I/O Map".)
Note The static RAM is indefinite at reset. Therefore, it should be initialized to zero at the beginning of the
program (RAM clear). This must be carried out for sure to avoid unexpected bugs.
Example Clear all the areas (00H to 3FH) of the static RAM (FFH remains in the HL register, however).
LOOP:
34
CHAPTER 4. INTERNAL CPU FUNCTIONS
MOV HL, #3FH
MOV A, #0H
MOV @HL, A: Clear (0) 00H to 3FH
DECS L
BR LOOP
DECS H
BR LOOP