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HT37B90 Arkusz danych(PDF) 9 Page - Holtek Semiconductor Inc |
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HT37B90 Arkusz danych(HTML) 9 Page - Holtek Semiconductor Inc |
9 / 80 page HT37B90/HT37B70/HT37B50/HT37B30 Rev.1.00 9 June22,2017 SystemArchitecture A key factor in the high-performance features of the Holtek range of Music Type microcontrollers is attrib- uted to the internal system architecture. The range of devices take advantage of the usual features found within RISC microcontrollers providing increased speed of operation and enhanced performance. The pipelining scheme is implemented in such a way that instruction fetching and instruction execution are overlapped, hence instructions are effectively executed in one cycle, with the exception of branch or call instructions. An 8-bit wide ALU is used in practically all operations of the in- struction set. It carries out arithmetic operations, logic operations, rotation, increment, decrement, branch de- cisions, etc. The internal data path is simplified by mov- ing data through the Accumulator and the ALU. Certain internal registers are implemented in the Data Memory and can be directly or indirectly addressed. The simple addressing methods of these registers along with addi- tional architectural features ensure that a minimum of external components is required to provide a functional I/O and A/D control system with maximum reliability and flexibility. ClockingandPipelining The main system clock, derived from either a Crys- tal/Resonator or RC oscillator. The oscillator frequency divided by 2 is subdivided into four internally generated non-overlapping clocks, T1~T4. The Program Counter is incremented at the beginning of the T1 clock during which time a new instruction is fetched. The remaining T2~T4 clocks carry out the decoding and execution functions. In this way, one T1~T4 clock cycle forms one instruction cycle. Although the fetching and execution of instructions takes place in consecutive instruction cy- cles, the pipelining structure of the microcontroller en- sures that instructions are effectively executed in one instruction cycle. The exception to this are instructions where the contents of the Program Counter are changed, such as subroutine calls or jumps, in which case the instruction will take one more instruction cycle to execute. When the RC oscillator is used, OSC2 is freed for use as a T1 phase clock synchronizing pin. This T1 phase clock has a frequency of fOSC/8 with a 1:3 high/low duty cycle. For instructions involving branches, such as jump or call instructions, two machine cycles are required to complete instruction execution. An extra cycle is required as the program takes one cycle to first obtain the actual jump or call address and then another cycle to actually execute the branch. The requirement for this extra cycle should be taken into account by pro- grammersintimingsensitiveapplications. ProgramCounter During program execution, the Program Counter is used to keep track of the address of the next instruction to be executed. It is automatically incremented by one each time an instruction is executed except for instructions, such as ²JMP² or ²CALL², that demand a jump to a non-consecutive Program Memory address. Note that the Program Counter width varies with the Program Memory capacity depending upon which device is se- lected. However, it must be noted that only the lower 8 bits, known as the Program Counter Low Register, are directlyaddressablebyuser. 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 f M C U ( f S Y S = f O S C / 2 ) P r o g r a m C o u n t e r P i p e l i n i n g T 1 T 2 T 3 T 4 T 1 T 2 T 3 T 4 T 1 T 2 T 3 T 4 SystemClockingandPipelining F e t c h I n s t . 1 E x e c u t e I n s t . 1 F e t c h I n s t . 2 F l u s h P i p e l i n e 1 2 3 4 5 6 D E L A Y : M O V A , [ 1 2 H ] C A L L D E L A Y C P L [ 1 2 H ] : : N O P E x e c u t e I n s t . 2 F e t c h I n s t . 3 F e t c h I n s t . 6 E x e c u t e I n s t . 6 F e t c h I n s t . 7 InstructionFetching |
Podobny numer części - HT37B90 |
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