Blinky on Lab-X1 twice as fast on 16F877 as on a 18F4550

[Ioannis]

Do you have any means to check the real frequency oscillator output that is going to the PIC?

Also, JP3 does no look that is is correctly connected. PIC should be on the midle pin and the jumper select either 4MHz or the CLK output of the chip U2.

If Y1A out pin is the PIC clock input, then this pin will always get 4MHz as the diagram shows no matter what the other jumpers are at.

Correct me if I am wrong, but on that diagram seems to me that way.

Ioannis

[Demon]

... Also, JP3 does no look that is is correctly connected. PIC should be on the midle pin and the jumper select either 4MHz or the CLK output of the chip U2.

If Y1A out pin is the PIC clock input, then this pin will always get 4MHz as the diagram shows no matter what the other jumpers are at.

Correct me if I am wrong, but on that diagram seems to me that way.

Ioannis

Y1A is not populated on the Lab-X1. You can add an IC if you wish to replace the default setup. Taken fron LABX1.TXT:

... To select a 20MHz clock, jumpers A and B should be on pins 1 and 2 and jumper C should be on pins 2 and 3.

Jumper JP3 (not populated) allows a crystal or TTL or CMOS oscillator to be used directly without the ISC502M clock generator. A TTL or CMOS oscillator, Y1A, may be used in place of crystal Y1 and the 2 capacitors, C5 and C6.

Having the jumper on the top 2 pins completes the circuit from ICS502M towards OSC1 (referred to as O1).

Robert