Jaroslav Pavlis

HC908GP32 Monitor Mode

Discussion created by Jaroslav Pavlis on Feb 28, 2007
Latest reply on Feb 28, 2007 by Jaroslav Pavlis
I can't get into monitor mode with GP32.

I have succesfully programmed new (blank) MCU. I have no developement board, so I used recommended circuit (from datasheet, page 130), internal oscillator with 32kHz crystal and direct serial connection (with MAX232 converter). It worked well.

But once the MCU is programmed, it's necessary to use an external oscillator, isn'it (datasheet, p.131)? So I made a simple oscillator with 9.830 MHz crystal and 74HC04. I attached an Vtst voltage to IRQ pin and changed the circuit according the schematic (page 130).

I tried to open a connection with CodeWarrior, Class 3, baudrate 9600. Only the first point "Hardware loopback detected" satisfied. I tried also an 4.9152 MHz crystal (with PTC3 low) with no effect.

Where could be the problem? Oscillator works, I checked it with an oscilloscope. Connection must be OK, because it works with another blank MCU and internal oscillator.

I think that my MCU doesn't work with external oscillator, because my user program (LED blinking) runs in normal mode only with internal oscillator. With external clock, the RST pin is permanently low and my program doesn't start.