Rainbow Electronics T89C5121 - Manual (Page 62)

62
A/T8xC5121
4164G–SCR–07/06
If a serial communication device (as described above: TWI or RS232) is detected, the
program download its content in the internal EEPROM and in CRAM.
Else, the program is internally downloaded from the internal EEPROM into the program
CRAM memory (16 Kbytes)
Then, in the two cases, the Bootloader executes a Long Jump at address 0000h which
initializes the Program counter at the lower address (0000h) of the executable CRAM.
Figure 24. CRAM with ROM and EEPROM Memory Mappings
T85C121 Code RAM Version Two memory blocks are implemented:
• The ROM memory contains the Bootloader program.
• The CRAM is the Application program memory.
After Reset, the program is downloaded, as described in last paragraph, from either an
external EEPROM or from an host connected on RS232 serial link into the program
CRAM memory of 16 Kbytes. Then the Program Counter is set at address 0000h of the
CRAM space and the program is executed.
16 Kbytes
256 bytes 0000h
3FFFh
CRAM XRAM RAM ROM
FFFFh
F800h
C000h
entry point
Bootloader
256 bytes