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Datenblatt-Suchmaschine für elektronische Bauteile |
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Datenblatt-Suchmaschine für elektronische Bauteile |
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HT82B40R Datenblatt(PDF) 36 Page - Holtek Semiconductor Inc |
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HT82B40R Datenblatt(HTML) 36 Page - Holtek Semiconductor Inc |
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36 / 54 page  HT82B40R/HT82B40A Rev. 1.70 36 November 5, 2014 Instruction Set Introduction Central to the successful operation of any microcontroller is its instruction set, which is a set of pro- gram instruction codes that directs the microcontroller to perform certain operations. In the case of Holtek microcontrollers, a comprehensive and flexible set of over 60 instructions is provided to enable programmers to implement their application with the minimum of pro- gramming overheads. For easier understanding of the various instruction codes, they have been subdivided into several func- tional groupings. Instruction Timing Most instructions are implemented within one instruc- tion cycle. The exceptions to this are branch, call, or ta- ble read instructions where two instruction cycles are required. One instruction cycle is equal to 4 system clock cycles, therefore in the case of an 8MHz system oscillator, most instructions would be implemented within 0.5 ms and branch or call instructions would be im- plemented within 1 ms. Although instructions which re- quire one more cycle to implement are generally limited to the JMP, CALL, RET, RETI and table read instruc- tions, it is important to realize that any other instructions which involve manipulation of the Program Counter Low register or PCL will also take one more cycle to imple- ment. As instructions which change the contents of the PCL will imply a direct jump to that new address, one more cycle will be required. Examples of such instruc- tions would be ²CLR PCL² or ²MOV PCL, A². For the case of skip instructions, it must be noted that if the re- sult of the comparison involves a skip operation then this will also take one more cycle, if no skip is involved then only one cycle is required. Moving and Transferring Data The transfer of data within the microcontroller program is one of the most frequently used operations. Making use of three kinds of MOV instructions, data can be transferred from registers to the Accumulator and vice-versa as well as being able to move specific imme- diate data directly into the Accumulator. One of the most important data transfer applications is to receive data from the input ports and transfer data to the output ports. Arithmetic Operations The ability to perform certain arithmetic operations and data manipulation is a necessary feature of most microcontroller applications. Within the Holtek microcontroller instruction set are a range of add and subtract instruction mnemonics to enable the necessary arithmetic to be carried out. Care must be taken to en- sure correct handling of carry and borrow data when re- sults exceed 255 for addition and less than 0 for subtraction. The increment and decrement instructions INC, INCA, DEC and DECA provide a simple means of increasing or decreasing by a value of one of the values in the destination specified. Logical and Rotate Operations The standard logical operations such as AND, OR, XOR and CPL all have their own instruction within the Holtek microcontroller instruction set. As with the case of most instructions involving data manipulation, data must pass through the Accumulator which may involve additional programming steps. In all logical data operations, the zero flag may be set if the result of the operation is zero. Another form of logical data manipulation comes from the rotate instructions such as RR, RL, RRC and RLC which provide a simple means of rotating one bit right or left. Different rotate instructions exist depending on pro- gram requirements. Rotate instructions are useful for serial port programming applications where data can be rotated from an internal register into the Carry bit from where it can be examined and the necessary serial bit set high or low. Another application where rotate data operations are used is to implement multiplication and division calculations. Branches and Control Transfer Program branching takes the form of either jumps to specified locations using the JMP instruction or to a sub- routine using the CALL instruction. They differ in the sense that in the case of a subroutine call, the program must return to the instruction immediately when the sub- routine has been carried out. This is done by placing a return instruction RET in the subroutine which will cause the program to jump back to the address right after the CALL instruction. In the case of a JMP instruction, the program simply jumps to the desired location. There is no requirement to jump back to the original jumping off point as in the case of the CALL instruction. One special and extremely useful set of branch instructions are the conditional branches. Here a decision is first made re- garding the condition of a certain data memory or indi- vidual bits. Depending upon the conditions, the program will continue with the next instruction or skip over it and jump to the following instruction. These instructions are the key to decision making and branching within the pro- gram perhaps determined by the condition of certain in- put switches or by the condition of internal data bits. |
Ähnliche Teilenummer - HT82B40R_14 |
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Ähnliche Beschreibung - HT82B40R_14 |
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