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HT98R068-1 Datasheet(PDF) 18 Page - Holtek Semiconductor Inc |
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HT98R068-1 Datasheet(HTML) 18 Page - Holtek Semiconductor Inc |
18 / 116 page Rev. 1.10 18 �e���a�� 1�� �01� Rev. 1.10 19 �e���a�� 1�� �01� HT98R068-1 Two Way Radio 8-Bit MCU HT98R068-1 Two Way Radio 8-Bit MCU Stack This is a special part of the memory which is used to save the contents of the Program Counter only. The stack 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. Pr og ra m Co un te r St ac k Le ve l 1 St ac k Le ve l 2 St ac k Le ve l 3 St ac k Le ve l 10 Pr og ra m Me mo ry T op of S ta ck St ac k Po in te r Bo tt om o f St ac k 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. 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 |
Similar Part No. - HT98R068-1_13 |
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Similar Description - HT98R068-1_13 |
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