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PIC16F688-I/ST 参数 Datasheet PDF下载

PIC16F688-I/ST图片预览
型号: PIC16F688-I/ST
PDF下载: 下载PDF文件 查看货源
内容描述: 14引脚基于闪存的8位CMOS微控制器采用纳瓦技术 [14-Pin Flash-Based, 8-Bit CMOS Microcontrollers with nanoWatt Technology]
分类和应用: 闪存微控制器
文件页数/大小: 202 页 / 3832 K
品牌: MICROCHIP [ MICROCHIP ]
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PIC16F688  
2.3.2  
STACK  
2.3  
PCL and PCLATH  
The PIC16F688 family has an 8-level x 13-bit wide  
hardware stack (see Figure 2-1). The stack space is  
not part of either program or data space and the Stack  
Pointer is not readable or writable. The PC is PUSHed  
onto the stack when a CALLinstruction is executed or  
an interrupt causes a branch. The stack is POPed in  
The Program Counter (PC) is 13 bits wide. The low byte  
comes from the PCL register, which is a readable and  
writable register. The high byte (PC<12:8>) is not  
directly readable or writable and comes from PCLATH.  
On any Reset, the PC is cleared. Figure 2-3 shows the  
two situations for the loading of the PC. The upper  
example in Figure 2-3 shows how the PC is loaded on a  
write to PCL (PCLATH<4:0> PCH). The lower exam-  
ple in Figure 2-3 shows how the PC is loaded during a  
CALLor GOTOinstruction (PCLATH<4:3> PCH).  
the event of a RETURN,  
RETLW or a RETFIE  
instruction execution. PCLATH is not affected by a  
PUSH or POP operation.  
The stack operates as a circular buffer. This means that  
after the stack has been PUSHed eight times, the ninth  
push overwrites the value that was stored from the first  
push. The tenth push overwrites the second push (and  
so on).  
FIGURE 2-3:  
LOADING OF PC IN  
DIFFERENT SITUATIONS  
PCH  
PCL  
Instruction with  
Note 1: There are no Status bits to indicate stack  
12  
8
7
0
PCL as  
overflow or stack underflow conditions.  
Destination  
PC  
2: There are no instructions/mnemonics  
called PUSH or POP. These are actions  
that occur from the execution of the  
CALL, RETURN, RETLW and RETFIE  
instructions or the vectoring to an  
interrupt address.  
8
PCLATH<4:0>  
PCLATH  
5
ALU Result  
PCH  
12 11 10  
PC  
PCL  
8
7
0
GOTO, CALL  
PCLATH<4:3>  
PCLATH  
11  
2
OPCODE<10:0>  
2.3.1  
COMPUTED GOTO  
A computed GOTOis accomplished by adding an offset  
to the program counter (ADDWF PCL). When perform-  
ing a table read using a computed GOTOmethod, care  
should be exercised if the table location crosses a PCL  
memory boundary (each 256-byte block). Refer to the  
Application Note AN556, “Implementing a Table Read”  
(DS00556).  
© 2007 Microchip Technology Inc.  
DS41203D-page 19  
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