UPD7554AA Просмотр технического описания (PDF) - NEC => Renesas Technology

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производитель

UPD7554AA

4-BIT SINGLE-CHIP MICROCOMPUTER

NEC => Renesas Technology 

µPD7554A, 7554A(A)

2.2 STACK POINTER (SP): 6 BITS

The stack pointer is a 6-bit register which retains head address information of the stack memory (LIFO type) which

is a part of the data memory.

Fig. 2-2 Stack Pointer Configuration

SP5 SP4 SP3 SP2 SP1 SP0 SP

The stack pointer is decremented when the call instruction is executed. It is incremented when the return

instruction is executed.

To determine the stack area, initialize the SP using the TAMSP instruction. Note that bit SP0 is loaded with 0

unconditionally when the TAMSP instruction is executed. Set the SP to the value of “the highest address of the stack

area + 1” because the stack operation starts with decrementation of the SP.

When the highest address of the stack area is 3FH which is the highest address of the data memory, the initial

value of SP5-0 must be 00H. For emulation using the µPD7500H (EVAKIT-7500B), set the data to be used for AM

when executing the TAMSP instruction.

Fig. 2-3 In Execution of TAMSP Instruction

A3

A2

A1

A0 (HL)3 (HL)2 (HL)1 (HL)0

0

SP5 SP4 SP3 SP2 SP1 SP0

Note that the contents of the SP cannot be read.

Caution Be sure to set the SP at the initial stage of the program execution because the SP becomes undefined

when the RESET signal is input.

Example

LHLI

LAI

ST

LAI

TAMSP

00H

0

4

;SP = 40H

16

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