EM73P982 datasheet(7/41 Pages) EMC

7 / 41 page

* This specification are subject to be changed without notice.

EM73P982

4-BIT MICROCONTROLLER

12.25.2001

HL REGISTER FUNCTION

(1) For instruction : LDL #k, LDH #k, THA, THL, INCL, DECL, EXAL, EXAH, HL register used as a

temporary register.

PROGRAM EXAMPLE: Load immediate data "5h" into L register, "Dh" into H register.

LDL #05h;

LDH #0Dh;

(2) For instruction LDAM, STAM, STAMI .., HL register used as a pointer for the address of RAM memory.

PROGRAM EXAMPLE: Store immediate data #Ah into RAM of address 35h.

LDL #5h;

LDH #3h;

STDMI #0Ah; RAM[35]

← Ah, LR←6

(3) For instruction : SELP, CLPL, TFPL, L regieter be a pointer to indicate the bit of I/O port.

When LR = 0 indicate P4.0

PROGRAM EXAMPLE: To set bit 0 of Port4 to "1"

LDL #00h;

SEPL ; P4.0

← 1

STACK POINTER (SP)

Stack pointer is a 4-bit register which stores the present stack level number.

Before using stack, user must set the SP value first, CPU will not initiate the SP value after reset condition.

When a new subroutine is accepted, the SP will be decreased one automatically, in another word, if

returning from a subroutine, the SP will be increased one.

The data transfer between ACC and SP is by instruction of "LDASP" and "STASP" at RAM bank0.

DATA POINTER (DP)

Data pointer is a 12-bit register which stores the address of ROM can indicate the ROM code data

specified by user (refer to data ROM).

EM73P982 Datasheet(PDF) 7 Page - ELAN Microelectronics Corp