PIC16F87T-E/ML【PDF 94/200 页】IC MCU FLASH 4KX14 EEPROM 28QFN

收藏本站

您好，
买卖IC网欢迎您。
请登录
免费注册

买卖IC网

Sheet目录3882

90页 91页 92页 93页 [94页]95页 96页 97页 98页

183

8008H–AVR–04/11

ATtiny48/88

19. Self-Programming the Flash

The device provides a Self-Programming mechanism for downloading and uploading program

code by the MCU itself. The Self-Programming can use any available data interface and associ-

ated protocol to read code and write (program) that code into the Program memory. The SPM

instruction is disabled by default but it can be enabled by programming the SELFPRGEN fuse

(to “0”).

The Program memory is updated in a page by page fashion. Before programming a page with

the data stored in the temporary page buffer, the page must be erased. The temporary page buf-

fer is filled one word at a time using SPM and the buffer can be filled either before the Page

Erase command or between a Page Erase and a Page Write operation:

Alternative 1, fill the buffer before a Page Erase:

Fill temporary page buffer

Perform a Page Erase

Perform a Page Write

Alternative 2, fill the buffer after Page Erase:

Perform a Page Erase

Fill temporary page buffer

Perform a Page Write

If only a part of the page needs to be changed, the rest of the page must be stored (for example

in the temporary page buffer) before the erase, and then be re-written. Alternative 1 provides an

effective Read-Modify-Write feature which allows the user software to first read the page, do the

necessary changes, and then write back the modified data. If alternative 2 is used, it is not pos-

sible to read the old data while loading since the page is already erased. The temporary page

buffer can be accessed in a random sequence. It is essential that the page address used in both

the Page Erase and Page Write operation is addressing the same page.

19.0.1

Performing Page Erase by SPM

To execute Page Erase, set up the address in the Z-pointer, write “00000011” to SPMCSR and

execute SPM within four clock cycles after writing SPMCSR. The data in R1 and R0 is ignored.

The page address must be written to PCPAGE in the Z-register. Other bits in the Z-pointer will

be ignored during this operation.

The CPU is halted during the Page Erase operation.

19.0.2

Filling the Temporary Buffer (Page Loading)

To write an instruction word, set up the address in the Z-pointer and data in R1:R0, write

“00000001” to SPMCSR and execute SPM within four clock cycles after writing SPMCSR. The

content of PCWORD in the Z-register is used to address the data in the temporary buffer. The

temporary buffer will auto-erase after a Page Write operation or by writing the CTPB bit in

SPMCSR. It is also erased after a system reset. Note that it is not possible to write more than

one time to each address without erasing the temporary buffer.

If the EEPROM is written in the middle of an SPM Page Load operation, all data loaded will be

lost.

发布紧急采购，3分钟左右您将得到回复。

采购需求

(若只采购一条型号，填写一行即可)

*型号	*数量	厂商	批号	封装

添加更多采购

采购需求

发布成功！您可以继续发布采购。也可以进入我的后台，查看报价

发布成功！您可以继续发布采购。也可以进入我的后台，查看报价

我的联系方式