The P89LPC900 (2)

In this second instalment we will look at the actual application of this microcontroller in greater detail. Notably the ‘in system programming’ functionality is described in detail. In addition, a practical design is presented that not only functions as a programmer for the controller, but as a prototyping board as well. As an example project, guided by an application note from Philips, a very good ADC can be built without requiring any additional peripherals.Flash memoryMany of you will recognise the ceramic microcontroller with a glass window. These are the UV erasable versions that were (and sometimes still are) used during the debugging stage of the application software. An expensive solution indeed, but the alternative, the burning of one-time programmable (OTP) devices was often more costly and far from flexible. The arrival of multi-time programmable flash (MTP) has made the UV-erasable type mostly obsolete. With that, the relatively long UV erasure time is now also a thing of the past.

In the circuit diagram and on the PCB, the RTS line is connected to pin 9 of 9-way sub-D connector K6. However, RTS should be connected to pins 7 and 8. The PCB layout has been modified accordingly (free download from our website).