LPC-H2106 Reset: How?

Development Boards MicroMod
1

I have the 40-pin header board for LPC2106. The data sheet says an external reset can be applied on Pin 3, but it doesn’t say how I do that. Do I need a circuit here to apply the reset? The schematic shows C4 (4.7uF) and R6 (10k) on the reset pin, are these parts already on the header board, or do I need to add that circuit externally? I tried jumpering Pin 3 to ground but that didn’t seem to do anything, help please?

2

What is in the schematic is built into the header board - it’s all already there.

This is your basic reset pulled high, cap debounce circuit. RST is active low, means you need to connect that pin to gnd momentarily to reset the chip.

The 10K connected to VCC pulls this pin high all the time (unless you have it tied directly to ground). The cap is there to debounce things when you attach your noisy reset switch. Do some googling on ‘reset switch circuits’.

-Nathan

3

Thanks for the reply. I moved on to trying to get JTAG working, and I think there is an error in the data sheet for LPC-H2106. The data sheet says to pull DBGSEL low to enable JTAG. But the LPC2106 MCU data sheet says low is for normal operation, high is for JTAG enable. Also, the LPC-2106 schematic shows DBGSEL tied to ground. And if I compare the LPC-P-2106 proto board with the JTAG enable, without the jumper it is grounded, with the jumper DBGSEL is high. This also jives with this JTAG connection shematic:

http://www.geocities.com/leon_heller/jtag.gif

So, isn’t the data sheet in error, DBGSEL (pin 2) should be should be high (tied to 3.3v pin 4) to enable JTAG? I finally realized this was backwards after 3 days of trying to get a connection to the LPC-H2106. Now ocdemon shows JTAG enabled with DBGSEL high at power up. Unfortunately, I’m getting bus errors now :frowning: I noticed some differences between Leon’s JTAG connection schematic above and the LPC-P2106 schematic.

Leon shows:

  • JTAG pin 5 connected to LPC2106 TDI

  • JTAG pin 7 connected to LPC2106 TMS

  • JTAG pin 9 connected to LPC2106 TCK

  • JTAG pin 13 connected to LPC2106 TDO

  • JTAG pin 15 connected to LPC2106 RST

  • LPC2106 DBGSEL connected to 3.3v

  • LPC2106 TRST connected to 3.3v

The LPC-P2106 proto board schematic differs, and it’s difficult to tell what the connections for JTAG should be for LPC-H2106. Can somebody tell me which JTAG pins connect to which pins on LPC-H2106?

Are the JTAG pins 15 (RST) and 11 (RTCK) not connected on the LPC-P-2106 and LPC-MT-2106? It’s difficult to tell from the schematic.

4

Does the JTAG have pin 8 and pin 15 on the DB-25 connected? That is required for the latest OCD Commander to work. Not sure about OCDemon, though.

Leon

5

Yep I checked the pin 8-15 connection with a meter. Since JTAG now seems to be enabled, but I’m getting bus errors, I decided to re-solder my circuit more carefully. Hopefully this will yield better results. Hey, thanks for sharing your info on the web. Had I not found your page I think I would have never had JTAG enabled :slight_smile: