# How is the board connected to this chip?

I have a dataflash memory that is too small to fit on a prototype board, so it has been put on a small board. I am having trouble figuring out where pin 1 is on this board. Below is a picture of the setup. The small circle on the chip is where pin 1 is. Underneath the large circles are the pins that connect to the board. Where on the board is pin 1? How do the lines connect to the memory? For the large circles on the right, how can they be connected to the chip if no lines can be seen going to them?

The pins on the dataflash memory are like this:

1. chip select
2. data output
3. write protect
4. ground
5. data input
6. clock
7. hold input
8. vcc


If I do a continuity test on pins 4 and 8, I should get continuity, right? What are pin combinations will work?

-

The tracks may be running underneath the chip, they may be obscured by soldermask, or they may be running on an inner layer of a multi-layer PCB.

Use a multimeter with a continuity checker to "buzz out" the connections. Test each leg of the chip against each pin on the board and draw out a map of what connects where.

Then, reference the datasheet and label the pins on your board.

For an Atmel dataflash chip, the legs are almost certainly numbered like this:

 | | | |
|4 3 2 1|
|      .|
|       |
|5 6 7 8|
| | | |


Here are the pictures from the AT45DB041D datasheet showing the pin arrangement and marker dot:

-
I'm not using the AT45 I'm using the W25Q80, which is similar. The legs are numbered in the same way, but the pin assignments are different. Is finding VCC and GND sufficient to know where everything else is? –  200ok404notfound Mar 13 '11 at 21:18
Yes, three points define a plane. So, you need to know which way up the chip is too ;) –  Toby Jaffey Mar 13 '11 at 21:20
I did a continuity test directly on the chip and found continuity between pins 5 and 8. That would be data input and Vcc. How is that possible? –  200ok404notfound Mar 13 '11 at 21:32
Use a continuity checker to check which pins on the IC match to which pins on the board. Checking the pins of the package itself is less useful. I do not know why pins 5 and 8 conduct. –  Toby Jaffey Mar 13 '11 at 21:38
Actually I made a mistake. It was touching something else. I was able to verify the pin connections to the board by putting one probe on a pin from the chip and the other probe on a pin from the board. I verified seven connections but it seems that pin 8, which is Vcc, is not connected. What kind of tool do I need to fix this? –  200ok404notfound Mar 13 '11 at 21:46
show 1 more comment

The tracks might not be visible under the solder mask. If you don't have any documentation you can work out the connections by checking continuity with a DVM.

-