參數(shù)資料
型號: 89C51ED2
廠商: Atmel Corp.
英文描述: 8-bit Flash Microcontroller
中文描述: 8位閃存微控制器
文件頁數(shù): 40/52頁
文件大?。?/td> 289K
代理商: 89C51ED2
Philips Semiconductors
Preliminary specification
89C51RB2/89C51RC2/
89C51RD2
80C51 8-bit Flash microcontroller family
16KB/32KB/64KB ISP/IAP Flash with 512B/512B/1KB RAM
1999 Sep 23
40
FFFF
C000
8000
4000
2000
0000
BLOCK 4
16 kB
BLOCK 3
16 kB
BLOCK 2
16 kB
BLOCK 1
8 kB
BLOCK 0
8 kB
PROGRAM
ADDRESS
BOOT ROM
(1 kB)
FFFF
FC00
SU01298
89C51RD2
89C51RC2
89C51RB2
Figure 43. Flash Memory Configurations
Power-On Reset Code Execution
The 89C51RB2/RC2/RD2 contains two special Flash registers: the
BOOT VECTOR and the STATUS BYTE. At the falling edge of reset,
the 89C51RB2/RC2/RD2 examines the contents of the Status Byte.
If the Status Byte is set to zero, power-up execution starts at
location 0000H, which is the normal start address of the user’s
application code. When the Status Byte is set to a value other than
zero, the contents of the Boot Vector is used as the high byte of the
execution address and the low byte is set to 00H. The factory
default setting is 0FCH, corresponds to the address 0FC00H for the
factory masked-ROM ISP boot loader. A custom boot loader can be
written with the Boot Vector set to the custom boot loader.
NOTE:
both bytes are erased at the same time. It is necessary
to reprogram the Boot Vector after erasing and
updating the Status Byte.
When erasing the Status Byte or Boot Vector,
Hardware Activation of the Boot Loader
The boot loader can also be executed by holding PSEN LOW,
EA greater than V
IH
(such as +5 V), and ALE HIGH (or not connected)
at the falling edge of RESET. This is the same effect as having a
non-zero status byte. This allows an application to be built that will
normally execute the end user’s code but can be manually forced
into ISP operation.
If the factory default setting for the Boot Vector (0FCH) is changed, it
will no longer point to the ISP masked-ROM boot loader code. If this
happens, the only way it is possible to change the contents of the
Boot Vector is through the parallel programming method, provided
that the end user application does not contain a customized loader
that provides for erasing and reprogramming of the Boot Vector and
Status Byte.
After programming the Flash, the status byte should be programmed
to zero in order to allow execution of the user’s application code
beginning at address 0000H.
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