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HT45R35 Datasheet(PDF) 8 Page - Holtek Semiconductor Inc |
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HT45R35 Datasheet(HTML) 8 Page - Holtek Semiconductor Inc |
8 / 59 page HT45R35 Rev. 1.30 8 May 14, 2010 by a return instruction, RET or RETI, the program counter is restored to its previous value from the stack. After a de- vice reset, the stack pointer will point to the top of the stack. If the stack is full and a non-masked interrupt takes place, the interrupt request flag will be recorded but the acknowledgment will be inhibited. When the stack pointer is decremented, by RET or RETI, the interrupt will be serviced. This feature prevents stack overflow al- lowing the programmer to use the structure more easily. In a similar case, if the stack is full and a ²CALL² is sub- sequently executed, stack overflow occurs and the first entry will be lost as only the most recent 4 return ad- dresses are stored. Data Memory - RAM The data memory has a capacity of 146 ´8 bits. The data memory is divided into two functional groups: special func- tion registers and general purpose data memory (120 ´8). Most are read/write, but some are read only. The general purpose data memory, addressed from 28H to 7FH at Bank 0 and from 40H to 5FH at Bank 1, is used for data and control information under instruction commands. All of the data memory areas can handle arithmetic, logic, increment, decrement and rotate operations di- rectly. Except for some dedicated bits, each bit in the data memory can be set and reset by the ²SET [m].i² and ²CLR [m].i² bit manipulation instructions. They are also indirectly accessible through the memory pointer registers (MP0;01H, MP1;02H). Bank 1 must be addressed indirectly using the memory pointer MP1 and the indirect addressing register IAR1. Any direct addressing or any indirect addressing using MP0 and IAR0 will always result in data from Bank 0 be- ing accessed. Indirect Addressing Register The method of indirect addressing allows data manipu- lation using memory pointers instead of the usual direct memory addressing method where the actual memory address is defined. Any action on the indirect address- ing registers will result in corresponding read/write oper- ations to the memory location specified by the corresponding memory pointers. This device contains two indirect addressing registers known as IAR0 and IAR1 and two memory pointers MP0 and MP1. Note that these indirect addressing registers are not physically implemented and that reading the indirect addressing registers indirectly will return a result of ²00H² and writ- ing to the registers indirectly will result in no operation. The two memory pointers, MP0 and MP1, are physically implemented in the data memory and can be manipu- lated in the same way as normal registers providing a convenient way with which to address and track data. When any operation to the relevant indirect addressing registers is carried out, the actual address that the microcontroller is directed to is the address specified by the related memory pointer. Bit 7 of the memory pointers are not implemented. How- ever, it must be noted that when the memory pointers in this device is read, a value of ²1² will be read. S p e c i a l P u r p o s e D a t a M e m o r y 0 0 H 0 1 H 0 2 H 0 3 H 0 4 H 0 5 H 0 6 H 0 7 H 0 8 H 0 9 H 0 A H 0 B H 0 C H 0 D H 0 E H 0 F H 1 0 H 1 1 H 1 2 H 1 3 H 1 4 H 1 5 H 1 6 H 1 7 H 1 8 H 1 9 H 1 A H 1 B H 1 C H 1 D H 1 E H 1 F H : U n u s e d R e a d a s " 0 0 " 2 0 H G e n e r a l P u r p o s e D a t a M e m o r y ( 8 8 B y t e s ) I n d i r e c t A d d r e s s i n g R e g i s t e r 0 M P 0 I n d i r e c t A d d r e s s i n g R e g i s t e r 1 M P 1 B P A C C P C L T B L P T B L H W D T S S T A T U S I N T C 0 T M R T M R C P A P A C P B P B C A S C R 0 A S C R 1 A S C R 2 I N T C 1 T M R A H T M R A L R C O C C R T M R B H T M R B L R C O C R 2 1 H 2 2 H 2 3 H 2 4 H 2 5 H 2 6 H 2 7 H 2 8 H 7 F H G e n e r a l P u r p o s e D a t a M e m o r y ( 3 2 B y t e s ) 4 0 H 5 F H R A M M a p p i n g B a n k 1 R A M M a p p i n g B a n k 0 RAM Mapping |
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