P89LPC925 PHILIPS [NXP Semiconductors], P89LPC925 Datasheet - Page 37

• Manufacturer Part Number: P89LPC925
• Description: 8-bit microcontrollers with accelerated two-clock 80C51 core 4 kB/8 kB 3 V low-power Flash with 8-bit A/D converter
• Manufacturer: PHILIPS [NXP Semiconductors]

Philips Semiconductors
9397 750 14471
Product data
Flash programming and erasing:
programming of the Flash memory that may be used. First, the Flash may be
programmed or erased in the end-user application by calling low-level routines
through a common entry point. Second, the on-chip ISP boot loader may be invoked.
This ISP boot loader will, in turn, call low-level routines through the same common
entry point that can be used by the end-user application. Third, the Flash may be
programmed or erased using the parallel method by using a commercially available
EPROM programmer which supports this device. Fourth, the Flash may be
programmed or erased using a commercially available EPROM programmer which
supports the ICP protocol. This device does not provide for direct verification of code
memory contents. Instead this device provides a 32-bit CRC result on either a sector
or the entire 4 kB/8 kB of user code space.
Boot ROM:
low-level details are handled by code that is contained in a Boot ROM that is separate
from the Flash memory. A user program simply calls the common entry point in the
Boot ROM with appropriate parameters to accomplish the desired operation. The
Boot ROM include operations such as erase sector, erase page, program page, CRC,
program security bit, etc. The Boot ROM occupies the program memory space at the
top of the address space from FF00 to FFFF hex, thereby not conflicting with the user
program memory space.
Power-on reset code execution:
elements: the Boot Vector and the Boot Status Bit. Following reset, the
P89LPC924/925 examines the contents of the Boot Status Bit. If the Boot Status Bit
is set to zero, power-up execution starts at location 0000H, which is the normal start
address of the user’s application code. When the Boot Status Bit is set to a one, the
contents of the Boot Vector is used as the high byte of the execution address and the
low byte is set to 00H. The factory default setting is 1FH for the P89LPC925 and
corresponds to the address 1F00H for the default ISP boot loader. The factory default
setting is 0FH for the P89LPC924 and corresponds to the address 0F00H for the
default ISP boot loader. This boot loader is pre-programmed at the factory into this
address space and can be erased by the user. Users who wish to use this loader
should take precautions to avoid erasing the 1 kB sector from 1C00H to 1FFFH
in the P89LPC925 or the 1 kB sector from 0C00H to 0FFFH in the P89LPC924.
Instead, the page erase function can be used to erase the eight 64-byte pages
which comprise the lower 512 bytes of the sector. A custom boot loader can be
written with the Boot Vector set to the custom boot loader, if desired.
Hardware activation of the boot loader:
forcing the device into ISP mode during a power-on sequence (see the
P89LPC924/925 User’s Manual for specific information). This has the same effect as
having a non-zero Boot Status Bit. This allows an application to be built that will
normally execute user code but can be manually forced into ISP operation. If the
factory default setting for the Boot Vector is changed, it will no longer point to the
factory pre-programmed ISP boot loader code. If this happens, the only way it is
possible to change the contents of the Boot Vector is through the parallel or ICP
programming methods, provided that the end user application does not contain a
customized loader that provides for erasing and reprogramming of the Boot Vector
and Boot Status Bit. After programming the Flash, the Boot Status Bit should be
programmed to zero in order to allow execution of the user’s application code
beginning at address 0000H.
When the microcontroller programs its own Flash memory, all of the
Rev. 03 — 15 December 2004
8-bit microcontrollers with accelerated two-clock 80C51 core
The P89LPC924/925 contains two special Flash
There are four methods of erasing or
The boot loader can also be executed by
P89LPC924/925
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
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