Philips 8-bit microcontroller with two-clock 80C51 core UM10109 Manual De Usuario

 

© Koninklijke Philips Electronics N.V. 2005. All rights reserved.

The P89LPC932A1 contains two special Flash elements: the BOOT VECTOR and the 
Boot Status Bit. Following reset, the P89LPC932A1 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 va 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 settings for this device is shown in 

, below. 

Note: These settings are different from the original P89LPC932.

The factory pre-programmed boot loader can be erased by the user. Users who wish to 
use this loader should take cautions to avoid erasing the last 1 kB sector on the device. 
Instead, the page erase function can be used to erase the eight 64-byte pages located in 
this sector. A custom boot loader can be written with the Boot Vector set to the custom 
boot loader, if desired.

The boot loader can also be executed by forcing the device into ISP mode during a 
power-on sequence (see 

). This is accomplished by powering up the device with 

the reset pin initially held low and holding the pin low for a fixed time after V

DD

 rises to its 

normal operating value. This is followed by three, and only three, properly timed low-going 
pulses. Fewer or more than three pulses will result in the device not entering ISP mode. 
Timing specifications may be found in the data sheet for this device.

This has the same effect as having a non-zero status bit. This allows an application to be 
built that will normally execute the 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 method, 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 status byte should be programmed to 
zero in order to allow execution of the user’s application code beginning at address 
0000H.

P89LPC932A1

8 kB 

× 8 

1FFFh

15h

DDh

1Fh

1 kB 

×  8

64 

× 8

1E00h to 1FFFh

1Fh

002aaa912

V

DD

RST

t

RL

t

VR

t

RH