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HT46R47E Datasheet(PDF) 9 Page - Holtek Semiconductor Inc |
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HT46R47E Datasheet(HTML) 9 Page - Holtek Semiconductor Inc |
9 / 73 page HT46R46E/C46E/R47E/C47E/R48AE/C48AE/R49E Rev. 1.20 9 August 15, 2007 Program Counter 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. For the Cost-Effective A/D Type series of microcontrollers, 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 directly addressable by user. When executing instructions requiring jumps to non-consecutive addresses such as a jump instruction, a subroutine call, interrupt or reset, etc., the microcontroller manages program control by loading the required address into the Program Counter. For condi- tional skip instructions, once the condition has been met, the next instruction, which has already been fetched during the present instruction execution, is dis- carded and a dummy cycle takes its place while the cor- rect instruction is obtained. The lower byte of the Program Counter, known as the Program Counter Low register or PCL, is available for program control and is a readable and writable register. By transferring data directly into this register, a short program jump can be executed directly, however, as only this low byte is available for manipulation, the jumps are limited to the present page of memory, that is 256 locations. When such program jumps are executed it should also be noted that a dummy cycle will be in- serted. The lower byte of the Program Counter is fully accessi- ble under program control. Manipulating the PCL might cause program branching, so an extra cycle is needed to pre-fetch. Further information on the PCL register can be found in the Special Function Register section. Mode Program Counter Bits b11 b10 b9 b8 b7 b6 b5 b4 b3 b2 b1 b0 Initial Reset 000000000000 External Interrupt 000000000100 Timer/Event Counter Overflow 000000001000 A/D Converter Interrupt 000000001100 Skip Program Counter + 2 Loading PCL PC11 PC10 PC9 PC8 @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: PC11~PC8: Current Program Counter bits @7~@0: PCL bits #11~#0: Instruction code address bits S11~S0: Stack register bits For the HT46R49E, the Program Counter is 12 bits wide, i.e. from b11~b0. For the HT46R47E and HT46R48AE, the Program Counter is 11 bits wide, i.e. From b10~b0, therefore the b11 column in the table is not applicable. For the HT46R46E, the Program Counter is 10 bits wide, i.e. from b9~b0, therefore the b11 and b10 the columns in the table are not applicable. |
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