having trouble programming/reading DS1393 (RTC)
Matthew
Posts: 200
Hello guys. I'm using the DS1393 RTC, and its datasheet can be found at:
http://pdfserv.maxim-ic.com/en/ds/DS1390-DS1393.pdf
My code is attached, and it's meant to read the 1/100th second register (page 13 in the datasheet has the registers).
My pins are hooked up in this manner (left side is pins from the DS1393) (page 10 in the datasheet has the pin assignments):
1-crystal
2-crystal
3-
4-PIN2
5-VSS
6-
7-PIN1
8-PIN0
9-
10-VCC
Do you all see anything wrong with the code? In the Debug screen, I see numbers increasing (Sometimes by 1, sometimes by 2, or sometimes random #'s/letters. They change like every 2-3 seconds). It's supposed to display 1/100ths of a second.
Any help will be greatly appreciated!
Thanks,
Matthew
http://pdfserv.maxim-ic.com/en/ds/DS1390-DS1393.pdf
My code is attached, and it's meant to read the 1/100th second register (page 13 in the datasheet has the registers).
My pins are hooked up in this manner (left side is pins from the DS1393) (page 10 in the datasheet has the pin assignments):
1-crystal
2-crystal
3-
4-PIN2
5-VSS
6-
7-PIN1
8-PIN0
9-
10-VCC
Do you all see anything wrong with the code? In the Debug screen, I see numbers increasing (Sometimes by 1, sometimes by 2, or sometimes random #'s/letters. They change like every 2-3 seconds). It's supposed to display 1/100ths of a second.
Any help will be greatly appreciated!
Thanks,
Matthew
bs2
398B
Comments
Does your 32.768kHz crystal have a 6pF load capacitance?
What are you testing this circuit on?
There are strict layout guidelines on page 12 for the placement
of the crystal. From personal experience with other time
keeping devices of this nature, there is enough parasitic
capacitance in a SSB to prevent your oscillator from working
properly.
Regardless of the crystal's operation, you should still be
able to communicate with the chip. Try enabling the square
wave output mode on page 16. If you don't have a scope, try
setting the rate select bits to something audible and try to
drive a piezo speaker. This should at least determine if
your crystal is oscillating or not.
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Beau Schwabe - Mask Designer III
National Semiconductor Corporation
(Communication Interface Division)
500 Pinnacle Court, Suite 525
Mail Stop GA1
Norcross,GA 30071
This is the crystal I'm using:
http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?Ref=349550&Row=77807&Site=US
The weird thing is that Digikey says it has a load capacitance of 6pF, however the datasheet says 12.5pF.
As far as the circuit, I'm just using the breadboard on a Homework board. The DS1393 was soldered onto a uSOP to DIP adapter (all of the connections were tested by a multimeter).
Check and make sure that the part you have in hand from the packing order sheet matches the 6pF
version you should have.
The SSB or Solderless BreadBoard used here will create too much parasitic capacitance for the
crystal to function properly. There is a solution using a SSB that allows you to stand-off the oscillator
from the SSB. I will try to post a picture, but basically you can use an 8-DIP wire wrap socket as an
adapter by bending only posts 1 & 2 of the socket at 90 deg ( the oscillator pins) and solder the crystal
directly to these posts as close to the base of the 90 deg bend as possible. (snip the excess post length
before soldering the crystal)
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Beau Schwabe - Mask Designer III
National Semiconductor Corporation
(Communication Interface Division)
500 Pinnacle Court, Suite 525
Mail Stop GA1
Norcross,GA 30071
Matthew