PIC 只要超過 4MHz 建議就選 HS Mode

再請教一下

因為我看datasheet上面寫 XT最大只到4MHZ

那我用20MHZ 選XT 會是20MHZ嗎??

這種事我也遇過
當時用的是18系列哪一顆忘了
也是本來HS可以過幾個月突然不行
改成XT就可以了

所以現在我全部都改成XT模式
免得又出問題...

參照：

1.板主我用的是4隻腳的振盪器 已經配好了
2.877A

另外 我懷疑是我的電路板有問題
因為我還有其他的板子 使用HS模式都沒問題 唯獨這一塊(打算重新layout新的板子 )

感覺是硬體出問題 不過我檢查過線路似乎是沒問題

1. 有可能阻抗及電容值 ( 20MHz 用 17~22pF) 沒配好，可以先燒成 Stand Alone Mode 量看看是否有震盪。
2. 請問是用哪一顆PIC?

使用20MHZ作為震盪頻率

然後選擇HS震盪模式

在PROGRAM TARGET DEVICE時

出現 ICD0083: Debug: Unable to enter debug mode. Please double click this message for more information.

詳細資料如下:
ICD0083: Debug: Unable to enter debug mode. Please double click this message for more information.

Description: MPLAB ICD 2 was unable to establish communications with the debug software on the target. This will prevent all debug operations (run, step, halt, breakpoint, etc.)

The MPLAB ICD 2 was unable to perform a debugging operation. There are numerous reasons why this might occur.

Top Ten Reasons Why You Can't Debug
The oscillator is not working. Check your configuration bits setting for the oscillator.
The target board is not powered. Check the power cable connection.
The MPLAB ICD 2 has somehow become physically disconnected from the PC. Check the USB or COM communication cable connection.
The MPLAB ICD 2 has somehow become physically disconnected from the target board. Check the communications cable connection.
The device is code-protected. Check your configuration bits setting for code protection.
MPLAB ICD 2 is selected as a programmer, and not as a debugger, in MPLAB IDE.
MPLAB ICD 2 to PC communications has somehow been interrupted. Reconnect to the ICD in MPLAB IDE.
The target application has somehow become corrupted or contains errors. For example, the regular linker script was used in the project instead of the MPLAB ICD 2 version of the linker script (e.g., 18F8722.lkr was used instead of 18F8722i.lkr). Try rebuilding and reprogramming the target application. Then initiate a power-on-reset of the target.
Other configuration settings are interferring with debugging. Any configuration setting that would prevent the target from executing code will also prevent the ICD from putting the code into debug mode.
MPLAB ICD 2 cannot always perform the action requested. For example, the ICD cannot set a breakpoint if the target application is currently running.

然後我把震盪模式改為XT 就可以了

會說這是個怪問題是因為 這個電路包含程式 之前都是用20MHZ和HS震盪模式

結果隔了幾個月 在拿出來使用時 出現此問題 百思不得其解

有人有遇過這種情形嗎??