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| 型号： | PIC17CXX |
| 厂商： | Microchip Technology Inc. |
| 英文描述： | EPROM Memory Programming Specification |
| 中文描述： | EPROM存储器编程规范 |
| 文件页数： | 36/71页 |
| 文件大小： | 1173K |
| 代理商： | PIC17CXX |
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1996 Microchip Technology Inc.
DS30412C-page 41
PIC17C4X
6.7
Program Counter Module
The Program Counter (PC) is a 16-bit register. PCL, the
low byte of the PC, is mapped in the data memory. PCL
is readable and writable just as is any other register.
PCH is the high byte of the PC and is not directly
addressable. Since PCH is not mapped in data or pro-
gram memory, an 8-bit register PCLATH (PC high latch)
is used as a holding latch for the high byte of the PC.
PCLATH is mapped into data memory. The user can
read or write PCH through PCLATH.
The 16-bit wide PC is incremented after each instruc-
tion fetch during Q1 unless:
Modied by GOTO, CALL, LCALL, RETURN, RETLW,
or RETFIE instruction
Modied by an interrupt response
Due to destination write to PCL by an instruction
“Skips” are equivalent to a forced NOP cycle at the
skipped address.
Figure 6-11 and Figure 6-12 show the operation of the
program counter for various situations.
FIGURE 6-11: PROGRAM COUNTER
OPERATION
FIGURE 6-12: PROGRAM COUNTER USING
THE CALL AND GOTO
INSTRUCTIONS
Internal data bus <8>
PCLATH
8
PCH
PCL
8
15
0
7
5 4
0
12
8 7
0
87
Last write
to PCLATH
PCLATH
Opcode
5
3
8
PCH
PCL
13
15
Using Figure 6-11, the operations of the PC and
PCLATH for different instructions are as follows:
a)
LCALL
instructions:
An 8-bit destination address is provided in the
instruction (opcode). PCLATH is unchanged.
PCLATH
→ PCH
Opcode<7:0>
→ PCL
b)
Read instructions on PCL:
Any instruction that reads PCL.
PCL
→ data bus → ALU or destination
PCH
→ PCLATH
c)
Write instructions on PCL:
Any instruction that writes to PCL.
8-bit data
→ data bus → PCL
PCLATH
→ PCH
d)
Read-Modify-Write instructions on PCL:
Any instruction that does a read-write-modify
operation on PCL, such as ADDWF PCL.
Read:
PCL
→ data bus → ALU
Write:
8-bit result
→ data bus → PCL
PCLATH
→ PCH
e)
RETURN
instruction:
PCH
→ PCLATH
Stack<MRU>
→ PC<15:0>
Using Figure 6-12, the operation of the PC and
PCLATH for GOTO and CALL instructions is a follows:
CALL
, GOTO instructions:
A 13-bit destination address is provided in the
instruction (opcode).
Opcode<12:0>
→ PC <12:0>
PC<15:13>
→ PCLATH<7:5>
Opcode<12:8>
→ PCLATH <4:0>
The read-modify-write only affects the PCL with the
result. PCH is loaded with the value in the PCLATH.
For example, ADDWF PCL will result in a jump within the
current page. If PC = 03F0h, WREG = 30h and
PCLATH = 03h before instruction, PC = 0320h after the
instruction. To accomplish a true 16-bit computed jump,
the user needs to compute the 16-bit destination
address, write the high byte to PCLATH and then write
the low value to PCL.
The following PC related operations do not change
PCLATH:
a)
LCALL
, RETLW, and RETFIE instructions.
b)
Interrupt vector is forced onto the PC.
c)
Read-modify-write instructions on PCL (e.g.BSF
PCL
).
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| PIC17LC42A-08/L | 功能描述:8位微控制器 -MCU 4KB 232 RAM 33 I/O RoHS:否 制造商:Silicon Labs 核心:8051 处理器系列:C8051F39x 数据总线宽度:8 bit 最大时钟频率:50 MHz 程序存储器大小:16 KB 数据 RAM 大小:1 KB 片上 ADC:Yes 工作电源电压:1.8 V to 3.6 V 工作温度范围:- 40 C to + 105 C 封装 / 箱体:QFN-20 安装风格:SMD/SMT |
| PIC17LC42A-08/P | 功能描述:8位微控制器 -MCU 4KB 232 RAM 33 I/O RoHS:否 制造商:Silicon Labs 核心:8051 处理器系列:C8051F39x 数据总线宽度:8 bit 最大时钟频率:50 MHz 程序存储器大小:16 KB 数据 RAM 大小:1 KB 片上 ADC:Yes 工作电源电压:1.8 V to 3.6 V 工作温度范围:- 40 C to + 105 C 封装 / 箱体:QFN-20 安装风格:SMD/SMT |
| PIC17LC42A-08/PQ | 功能描述:8位微控制器 -MCU 4KB 232 RAM 33 I/O RoHS:否 制造商:Silicon Labs 核心:8051 处理器系列:C8051F39x 数据总线宽度:8 bit 最大时钟频率:50 MHz 程序存储器大小:16 KB 数据 RAM 大小:1 KB 片上 ADC:Yes 工作电源电压:1.8 V to 3.6 V 工作温度范围:- 40 C to + 105 C 封装 / 箱体:QFN-20 安装风格:SMD/SMT |
| PIC17LC42A-08/PT | 功能描述:8位微控制器 -MCU 4KB 232 RAM 33 I/O RoHS:否 制造商:Silicon Labs 核心:8051 处理器系列:C8051F39x 数据总线宽度:8 bit 最大时钟频率:50 MHz 程序存储器大小:16 KB 数据 RAM 大小:1 KB 片上 ADC:Yes 工作电源电压:1.8 V to 3.6 V 工作温度范围:- 40 C to + 105 C 封装 / 箱体:QFN-20 安装风格:SMD/SMT |
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