Datasheet

14
7764A–8051–11/07
2. In-System Programming (ISP)
The In-System Programming feature will be referenced as ISP in the rest of the document.
Most of Atmel’s C51 devices support the ISP mode. This feature enables the user to program
the device directly on his application without having to unsolder the device or using an external
programmer. This feature is made by means of a bootloader firmware embedded in the device
itself. A PC based application like FLIP (FLexible In-system Programmer) or any equivalent cus-
tom software enables to communicate with the bootloader to perform the part programming.
FLIP can be downloaded free of charge from the Atmel’s web site. It supports different interfaces
like RS232, USB, and CAN following the used device. Ensure you are always using the latest
version of FLIP.
The ISP mode is invoked by applying an hardware condition. The hardware condition differs
between a HPC and a LPC package (See “Type of package” on page 3.)
2.1 HPC package
2.1.1 Hardware settings
The following hardware settings must be applied in normal mode (execution) before starting the
ISP mode (programming).
• EA pin must be tied to Vcc. The bootloader is only active when internal program memory is
used.
• ALE pin cannot be forced by an external signal. This pin is driven by the MCU. Leave this pin
unconnected if not used.
• PSEN pin cannot be forced by an external signal. This pin is driven by the MCU. Leave this
pin unconnected if not used.
2.1.2 Starting the ISP mode
Software condition: there are some configuration bits available in the part which enables to con-
figure the bootloader behaviour. Refer to the product’s bootloader datasheet for further
information. These bits are accessible from the GUI of FLIP. The BLJB bit is part of these. Most
of the time, it is activated at manufacturing level on new chips to have the device run in ISP
mode at first power on. When the BLJB is active, the user does not need to apply the hardware
condition described here after. It may be usefull at production level for instance. The BLJB bit is
deactivated by the bootloader after the first programming. It is then the responsability of the user
to re-activate it.
Hardware condition: when the BLJB bit is inactive, the only way to have the device run in ISP
mode, is to apply the hardware condition.
The hardware condition consists to apply an hardware reset while pulling the PSEN pin to
ground then to release the PSEN pin once the hardware reset has been applied.
It is recommended to pull the PSEN pin to ground through a 1K resistor to prevent the PSEN pin
from being damaged.
WARNING
Do not apply the hardware condition at power up otherwise the ISP mode may fail to start.
The hardware condition must be applied only when the device has started and when the
power supplies are stables.