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HT82K95E Datasheet(PDF) 6 Page - Holtek Semiconductor Inc |
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HT82K95E Datasheet(HTML) 6 Page - Holtek Semiconductor Inc |
6 / 42 page Functional Description HT82K95E/HT82K95A Rev. 2.40 6 November 5, 2014 Execution Flow The system clock for the microcontroller is derived from a crystal. The system clock is internally divided into four non-overlapping clocks. One instruction cycle consists of four system clock cycles. Instruction fetching and execution are pipelined in such a way that a fetch takes an instruction cycle while de- coding and execution takes the next instruction cycle. However, the pipelining scheme allows each instruction to be effectively executed in a cycle. If an instruction changes the program counter, two cycles are required to complete the instruction. Program Counter - PC The program counter (PC) controls the sequence in which the instructions stored in the program ROM are executed and its contents specify a full range of pro- gram memory. After accessing a program memory word to fetch an in- struction code, the contents of the program counter are incremented by one. The program counter then points to the memory word containing the next instruction code. When executing a jump instruction, conditional skip ex- ecution, loading PCL register, subroutine call or return from subroutine, initial reset, internal interrupt, external interrupt or return from interrupts, the PC manipulates the program transfer by loading the address corre- sponding to each instruction. The conditional skip is activated by instructions. Once the condition is met, the next instruction, fetched during the current instruction execution, is discarded and a dummy cycle replaces it to get the proper instruction. Otherwise proceed to the next instruction. The lower byte of the program counter (PCL) is a read- able and writeable register (06H). Moving data into the PCL performs a short jump. The destination will be within the current program ROM page. When a control transfer takes place, an additional dummy cycle is required. T 1 T 2 T 3 T 4 T 1 T 2 T 3 T 4 T 1 T 2 T 3 T 4 F e t c h I N S T ( P C ) E x e c u t e I N S T ( P C - 1 ) F e t c h I N S T ( P C + 1 ) E x e c u t e I N S T ( P C ) F e t c h I N S T ( P C + 2 ) E x e c u t e I N S T ( P C + 1 ) P C P C + 1 P C + 2 S y s t e m C l o c k O S C 2 ( R C o n l y ) P C Execution Flow Mode Program Counter *11 *10 *9 *8 *7 *6 *5 *4 *3 *2 *1 *0 Initial reset 000000000000 USB interrupt 000000000100 Timer/Event Counter 0 overflow 000000001000 Timer/Event Counter 1 overflow 000000001100 Skip Program Counter+2 Loading PCL *11 *10 *9 *8 @7 @6 @5 @4 @3 @2 @1 @0 Jump, call branch #11 #10 #9 #8 #7 #6 #5 #4 #3 #2 #1 #0 Return from subroutine S11 S10 S9 S8 S7 S6 S5 S4 S3 S2 S1 S0 Program Counter Note: *11~*0: Program counter bits S11~S0: Stack register bits #11~#0: Instruction code bits @7~@0: PCL bits |
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Similar Description - HT82K95E_14 |
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