Rainbow Electronics DS89C450 User Manual
Page 25
DS89C430/DS89C440/DS89C450 Ultra-High-Speed Flash Microcontrollers
25 of 48
ROM Loader
The full on-chip flash program memory space, security flash block, and external SRAM can be programmed in-
system from an external source through serial port 0 under the control of a built-in ROM loader. The ROM loader
also has an auto-baud feature that determines which baud-rate frequencies are being used for communication and
sets the baud-rate generator for that speed.
When the DS89C430 is powered up and has entered its user operating mode, the ROM loader mode can be
invoked at any time by forcing RST = 1,
EA = 0, and PSEN = 0. It remains in effect until power-down or when the
condition (RST = 1 and
PSEN = EA = 0) is removed. Entering the ROM loader mode forces the processor to start
fetching from the 2kB internal ROM for program memory initialization and other loader functions.
The read/write accessibility is determined by the state of the lock bits, which can be verified directly by the ROM
loader.
The flash memory can be programmed (by the built-in ROM loader) using commands that are received over the
serial interface from a host PC. Full details of the ROM loader commands are given in the Ultra-High-Speed Flash
Microcontroller User’s Guide. Host software to communicate with the ROM loader is available in Windows
®
format
as well as other platforms. Contact our technical support department at
for more
information.