Microcontroller Programming
T8xC5121 Starter Kit User Guide
4-13
4186E–SCR–05/04
4.2.3
Using Pre-
programmed Parts
If neither AT24C128 External EEPROM nor RS-232 programming has been detected,
the on-chip ROM Bootloader downloads the internal EEPROM content (16K bytes) in
the Code RAM and runs the corresponding program.
Note:
This assumes that, previously, the T89C5121 microcontroller has been pro-
grammed.
After reset, execution of the program takes 4 seconds at 14.7456 MHz.
4.3
Programming the
T85C5121
The T85C5121 version can be loaded in CRAM with the application program and exe-
cuted once connected to the Demonstration Board. See Figure 2-2.
The processes are the same as for T89C5121 (RS-232 and External EEPROM) except
that there is not an internal EEPROM and so the standalone configuration is not valid.
4.3.1
Programming from
External EEPROM
Source for SSPO24
package
After Reset, if an AT24C128 EEPROM has been detected at U1 (see Figure 4-4), the
on-chip ROM Bootloader downloads the external EEPROM content (16K bytes) in the
Code RAM.
Figure 4-4. EEPROM at U1 of Demonstration Board
4.3.2
Programming from
External EEPROM
Source for PLCC52
package
The PLCC52 Package Product can be programmed using either :
External EEPROM Atmel AT24C128 at U6 location
External EEPROM Atmel AT24C128 at U1 location
Serial RS-232
The two last processes are the same as for T89C5121 (RS-232 and External
EEPROM).
The first process can use an external EEPROM which is seen by the Bootloader as the
Internal EEPROM of the AT89C5121 Product version.
Internal
on-chip
EEPROM
Code
RAM
16K bytes
T89C5121
