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BR8F 参数 Datasheet PDF下载

BR8F图片预览
型号: BR8F
PDF下载: 下载PDF文件 查看货源
内容描述: [400mA 8.0kV 100nS High Voltage Medium and High Current Diodes]
分类和应用:
文件页数/大小: 58 页 / 442 K
品牌: HOLTIC [ HOLT INTEGRATED CIRCUITS ]
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HT46R01A  
Program Counter  
to pre-fetch. Further information on the PCL register can  
be found in the Special Function Register section.  
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  
directly addressable by user.  
Stack  
This is a special part of the memory which is used to  
save the contents of the Program Counter only. The  
stack has 4 levels and is neither part of the data nor part  
of the program space, and is neither readable nor  
writable. The activated level is indexed by the Stack  
Pointer, SP, and is neither readable nor writeable. At a  
subroutine call or interrupt acknowledge signal, the con-  
tents of the Program Counter are pushed onto the stack.  
At the end of a subroutine or an interrupt routine, sig-  
naled by a return instruction, RET or RETI, the Program  
Counter is restored to its previous value from the stack.  
After a device reset, the Stack Pointer will point to the  
top of the stack.  
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.  
If the stack is full and an enabled interrupt takes place,  
the interrupt request flag will be recorded but the ac-  
knowledge signal 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.  
However, when the stack is full, a CALL subroutine in-  
struction can still be executed which will result in a stack  
overflow. Precautions should be taken to avoid such  
cases which might cause unpredictable program  
branching.  
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 writeable regis-  
ter. 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.  
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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  
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Program Counter Bits  
Mode  
b9  
0
b8  
0
b7  
0
b6  
0
b5  
0
b4  
0
b3  
0
b2  
0
b1  
0
b0  
0
Initial Reset  
External Interrupt  
Timer/Event Counter Overflow  
A/D Converter Interrupt  
Skip  
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
1
1
0
0
Program Counter + 2  
Loading PCL  
PC9  
#9  
PC8  
#8  
@7  
#7  
@6  
#6  
@5  
#5  
@4  
#4  
@3  
#3  
@2  
#2  
@1  
#1  
@0  
#0  
Jump, Call Branch  
Return from Subroutine  
S9  
S8  
S7  
S6  
S5  
S4  
S3  
S2  
S1  
S0  
Program Counter  
Note: PC9~PC8: Current Program Counter bits  
@7~@0: PCL bits  
#9~#0: Instruction code address bits  
S9~S0: Stack register bits  
Rev. 1.10  
7
August 13, 2008  
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