at83c5122 ATMEL Corporation, at83c5122 Datasheet - Page 27

• Manufacturer Part Number: at83c5122
• Description: At83c5123 C51 Microcontroller With Usb And Smart Card Reader Interfaces
• Manufacturer: ATMEL Corporation

4202E–SCR–06/06
When pin EA =1 and after the reset, the MCU begins the execution of the embedded
bootloader from location F800h of the ROM. The bootloader implements an In-System
Programming (ISP) mode which manages the transfer of the code in the volatile Pro-
gram Memory (CRAM).
For CRAM version, the code is supplied by the ATMEL’s FLexible In-system Program-
ming software (FLIP) through USB or UART interface
For E2PROM version, the code is supplied from the internal code E2PROM or by FLIP.
The state of pin P3.7 at reset determines the code source. If P3.7=1 (reset condition)
the source is the internal E2PROM and the transfer takes about 1.5 seconds. If P3.7=0
the source is FLIP and the transfer time depends mainly on external conditions not
related to bootloader.
Once the code is running in CRAM, the roll-over condition (code fetched beyond
address 7FFFh) depends on the state of ENBOOT bit of AUXR1 register (Table 6 on
page 25).
If ENBOOT=1 (reset condition) the MCU fetches the code from bootloader ROM. If
ENBOOT=0, the MCU fetches the code from the external Program Memory. In this last
case, PSEN is activated and Ports P0 and P2 are used to emit data and address
signals.
Warning : external Program Memory access is not allowed on Low Pin Count
Packages.
7EFFh
FFFFh
7FFFh
7F00h
0000h
AT8xC5122 Microcontroller
Bootloader
User code
Reserved
P3.7
AT8xC5122/23
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