HT67F60 datasheet(33/242 Pages) HOLTEK

33 / 242 page

HT67F30/HT67F40/HT67F50/HT67F60

TinyPowerTM A/D Flash Type 8-Bit MCU with LCD & EEPROM

Rev. 1.50

March 06 , 2012

Rev. 1.50

March 06 , 2012

Stack

This is a special part of the memory which is used to save the contents of the Program Counter only.

The stack has multiple levels depending upon the device and is neither part of the data nor part of

the program space, and is neither readable nor writeable. The activated level is indexed by the Stack

Pointer, and is neither readable nor writeable. At a subroutine call or interrupt acknowledge signal,

the contents of the Program Counter are pushed onto the stack. At the end of a subroutine or an

interrupt routine, signaled by a return instruction, RET or RETI, the Program Counter is restored to

its previous value from the stack. After a device reset, the Stack Pointer will point to the top of the

stack.

If the stack is full and an enabled interrupt takes place, the interrupt request flag will be recorded but

the acknowledge signal will be inhibited. When the Stack Pointer is decremented, by RET or RETI,

the interrupt will be serviced. This feature prevents stack overflow allowing the programmer to use

the structure more easily. However, when the stack is full, a CALL subroutine instruction can still be

executed which will result in a stack overflow. Precautions should be taken to avoid such cases

which might cause unpredictable program branching.

If the stack is overflow, the first Program Counter save in the stack will be lost.

Pr ogr am C ount er

St a ck Lev el 1

St a ck Lev el 2

St a ck Lev el 3

St a ck Lev el N

Pr ogr am

Me mo ry

To p of S ta ck

St ac k

Po in te r

Bo tto m of S ta ck

Device

Stack Levels

HT67F30

HT67F40/HT67F50

HT67F60

Arithmetic and Logic Unit – ALU

The arithmetic-logic unit or ALU is a critical area of the microcontroller that carries out arithmetic

and logic operations of the instruction set. Connected to the main microcontroller data bus, the ALU

receives related instruction codes and performs the required arithmetic or logical operations after

which the result will be placed in the specified register. As these ALU calculation or operations may

result in carry, borrow or other status changes, the status register will be correspondingly updated to

reflect these changes. The ALU supports the following functions:

● Arithmetic operations: ADD, ADDM, ADC, ADCM, SUB, SUBM, SBC, SBCM, DAA

● Logic operations: AND, OR, XOR, ANDM, ORM, XORM, CPL, CPLA

● Rotation RRA, RR, RRCA, RRC, RLA, RL, RLCA, RLC

● Increment and Decrement INCA, INC, DECA, DEC

● Branch decision, JMP, SZ, SZA, SNZ, SIZ, SDZ, SIZA, SDZA, CALL, RET, RETI

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