HT827A0 データシートの表示（PDF） - Holtek Semiconductor

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HT827A0

8-Bit Microcontroller with Voice ROM

Holtek Semiconductor 

HT827A0

· Table location

Any location in the program ROM can be used

as a look-up table. The instructions

²TABRDC [m]² (the current page, 1 page=256

words) and ²TABRDL [m]² (the last page)

transfer the contents of the lower-order byte

to the specified data memory, and the

higher-order byte to TBLH (08H). Only the

destination of the lower-order byte in the ta-

ble is well-defined. The other bits of the table

word are transferred to the lower portion of

TBLH. The higher-order byte register

(TBLH) of the table is read only. The table

pointer (TBLP), on the other hand, is a

read/write register (07H) indicating the table

location. This location must be placed in

TBLP before accessing the table. All the table

related instructions require 2 cycles to com-

plete an operation. These areas may function

as a normal program memory depending

upon the user¢s requirements.

Stack register - Stack

The stack register is a special part of the mem-

ory used to save the contents of the program

counter (PC). This stack is organized into 8 lev-

els. It is neither part of the data nor program

space, and cannot be read or written to. Its acti-

vated level is indexed by a stack pointer (SP)

and cannot be read or written to. At a subrou-

tine call or interrupt acknowledgment, the con-

tents of the program counter are pushed onto

the stack. The program counter is restored to

its previous value from the stack at the end of a

subroutine or interrupt routine, which is sig-

naled by a return instruction (RET or RETI).

After a chip resets, SP will point to the top of

the stack.

The interrupt request flag will be recorded but

the acknowledgment will be inhibited when the

stack is full and a non-masked interrupt takes

place. After the stack pointer is decremented

(by RET or RETI), the interrupt will be ser-

viced. This feature prevents stack overflow and

allows programmers to use the structure more

easily. In a similar case, if the stack is full and a

²CALL² is subsequently executed, stack over-

flow occurs and the first entry is lost.

Data memory - RAM

The data memory is further divided into two

functional groups, namely, special function reg-

isters and general purpose data memories. Al-

though most of them can be read or be written

to, some are read only.

The data memory size for HT827A0 is shown as

follows.

Pard No.

Special

General

RAM RAM Address

HT827A0 00H~2FH

30H~FFH

The special function registers include an indi-

rect addressing register (00H), timer/event

counter high byte register (TMRH; 0FH),

timer/event counter low byte register (TMRL;

10H); timer/event counter control register

(TMRC; 11H), program counter lower-order

byte register (PCL; 06H), memory pointer reg-

ister (MP; 01H), accumulator (ACC; 05H), table

pointer (TBLP; 07H), table higher-order byte

register (TBLH; 08H), status register

(STATUS; 0AH), interrupt control register

(INTC; 0BH), watchdog timer option setting

register (WDTS; 09H), I/O registers (PA; 12H,

PB; 14H, PC; 16H, PD; 18H, PE; 1AH) and I/O

Table Location

Instruction(s)

*12 *11 *10 *9 *8 *7 *6 *5 *4 *3 *2 *1 *0

TABRDC [m] P12 P11 P10 P9 P8 @7 @6 @5 @4 @3 @2 @1 @0

TABRDL [m] 1 1 1 1 1 @7 @6 @5 @4 @3 @2 @1 @0

Note: *12~*0: Bits of table location

@7~@0: Bits of table pointer

Table location

P12~P8: Bits of current program counter

10

March 15, 2000

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