UPD7564ACSA datasheet(14/56 Pages) NEC

14 / 56 page

µPD7564A, 7564A(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

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

(HL)3

(HL)2

(HL)1

(HL)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

00H

LAI

TAMSP

;SP = 40H

UPD7564ACSA Datasheet(PDF) 14 Page - NEC

UPD7564ACSA Datasheet(HTML) 14 Page - NEC

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56

Datasheet Download

Link URL