PDA

View Full Version : Seeking info on chip/chip differences re peripheral functions



LarryP
02-07-2013, 02:17 PM
Greetings all,

Please forgive me if I've missed something obvious, but I'm having some trouble understanding which peripherals are present in the specific chip used in Teensy3 and what pins they can connect to. The datasheet covers several chips, and they don't all have the same peripherals instantiated. While there are tables, etc., documenting the chip/chip differences re memory, I haven't found anything similar in the datasheet clearly detailing the chip/chip differences in peripherals. I'd like to know which peripherals we have on our K20 chip (and also which are available on other K20 parts.) Is there some companion document or documents with this sort of info?:confused:


Here's are two examples to clarify what sort of info I'd like to find:

(1) In section 31.2.3, the datasheet states:


In some packages, VREFH is connected in the package to VDDA and VREFL to VSSA.

OK, but are they connected that way in our chip, or not? (If I had a bare chip and very steady hands, I could ohm it out.) Is info about this sort of chip/chip difference re peripherals absent from the datasheet, or have I missed something?


(2) Section 32.3 describes a 6-bit DAC and some related signals, e.g. DACEN. However, I cannot find "DAC" or "DAC*" in the pinout table (in sect. 10.3.2, p.193 or in the package diagrams like Fig. 10.2 on p. 197), not only for the 64 pin package (as is our chip), but not for **any** K20 chip or package! So, is the DAC feature present in any of the chips this datasheet covers? If so, how can we tell? I'd expect DAC, DAC*, D2A or D2A* to appear somewhere in the pinout table for at least on of the chips this datasheet covers. However, searching the pinout section for any of those strings finds nothing in the pinout section at all. So, does the DAC appear in any of these chips? If so, which one(s)? That's the sort of information I'd like to find.

If any of you reading knows where this sort of chip to chip differences re peripherals is documented, please post here.

Thanks,

Larry

Jp3141
02-07-2013, 03:22 PM
Greetings all,

Please forgive me if I've missed something obvious, but I'm having some trouble understanding which peripherals are present in the specific chip used in Teensy3 and what pins they can connect to. The datasheet covers several chips, and they don't all have the same peripherals instantiated. While there are tables, etc., documenting the chip/chip differences re memory, I haven't found anything similar in the datasheet clearly detailing the chip/chip differences in peripherals. I'd like to know which peripherals we have on our K20 chip (and also which are available on other K20 parts.) Is there some companion document or documents with this sort of info?:confused:


Here's are two examples to clarify what sort of info I'd like to find:

(1) In section 31.2.3, the datasheet states:



OK, but are they connected that way in our chip, or not? (If I had a bare chip and very steady hands, I could ohm it out.) Is info about this sort of chip/chip difference re peripherals absent from the datasheet, or have I missed something?


(2) Section 32.3 describes a 6-bit DAC and some related signals, e.g. DACEN. However, I cannot find "DAC" or "DAC*" in the pinout table (in sect. 10.3.2, p.193 or in the package diagrams like Fig. 10.2 on p. 197), not only for the 64 pin package (as is our chip), but not for **any** K20 chip or package! So, is the DAC feature present in any of the chips this datasheet covers? If so, how can we tell? I'd expect DAC, DAC*, D2A or D2A* to appear somewhere in the pinout table for at least on of the chips this datasheet covers. However, searching the pinout section for any of those strings finds nothing in the pinout section at all. So, does the DAC appear in any of these chips? If so, which one(s)? That's the sort of information I'd like to find.

If any of you reading knows where this sort of chip to chip differences re peripherals is documented, please post here.

Thanks,

Larry

There are 3 main documents describing the part used in Teensy 3.0 -- this part is MK20DX128VLH5 (it is part of the K20_50 , and the documents on Freescale's site are the K20P64M50SF0 sub-family data sheet and the reference manual. ARM supply the CPU reference. The relevant link for Freescale is http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=K20_50&fpsp=1&tab=Documentation_Tab

The Family Reference Manual describes all (most, for instance the ARM manual describes the Interrupt Controller because it is part of the CPU) of the CPU's peripherals -- e.g. the ADC, timers etc. Specific details (which might differer from product to product) are in the Data Sheet which is at http://cache.freescale.com/files/32bit/doc/data_sheet/K20P64M50SF0.pdf?fpsp=1 . The pinout is in this (page 52 and it shows that (in our 64 LQFP package version) VREFH is separate from VDDA (pins 14 and 13 respectively). Now in Teensy's schematic ( http://forum.pjrc.com/attachment.php?attachmentid=40&d=1353025154) you can see that VREFH is connected to the Teensy AREF pin, and to VDDA via 470 ohm -- basically, if you don't connect to it, it will get VDDA, but you can drive it to your own reference if needed.

Yes, there is a DAC in the IC, but it is not pinned out -- it is an internal connection (reference) for the Comparator (see the book !!).

It is complicated, but that it because there are many products using the same internal chip and each has many many features which need very detailed descriptions.

LarryP
02-07-2013, 05:25 PM
@Jp3141,

Thanks much for the pointers to the other documents.

FYI, from the links you provided, I found the following table to be the closest to what I was looking for:

http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=K20_50&tab=Buy_Parametric_Tab&fromSearch=false#2

On that webpage, search for the exact P/N (MK20DX128VLH5) and you'll find a table describing most of the differences among the K20_50 subSubFamily. Note: on this webpage, on the extreme right and at the top of the table (next to the column descriptions) is a little arrow labelled "more." Clicking that gives a more columns of info, such as number of PWM channels. However, even after clicking on the "more" button, I don't see nearly as many features listed in this table as there are described in the 1200+ page datasheet.

Does anybody reading here know whether features not explicitly mentioned in this table (for instance CRC or RTC) are present in all K20_50 chips? (Neither term seems to be evident on that webpage.) In the case of the RTC, we know from *Paul's documentation* that our chip really has the RTC implemented and brought out to pins. From Freescale's docs, that info seems only evident from scrutinizing the pinout table. (And for the CRC unit, which has no associated pins, its presence/absence is even less clear, to me at least.) I'm getting a headache looking through all the alternate functions on all the pins of our chip; such is tech life....

One interesting thing listed is the budgetary price for these chips in quantity 1000, $2.58 each. I'm still amazed how bang per buck continues to increase.

Thanks again for the links to the other documents; I really appreciate it!

Jp3141
02-07-2013, 07:25 PM
@Jp3141,

Thanks much for the pointers to the other documents.

FYI, from the links you provided, I found the following table to be the closest to what I was looking for:

http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=K20_50&tab=Buy_Parametric_Tab&fromSearch=false#2

Does anybody reading here know whether features not explicitly mentioned in this table (for instance CRC or RTC) are present in all K20_50 chips? (Neither term seems to be evident on that webpage.) In the case of the RTC, we know from *Paul's documentation* that our chip really has the RTC implemented and brought out to pins. From Freescale's docs, that info seems only evident from scrutinizing the pinout table. (And for the CRC unit, which has no associated pins, its presence/absence is even less clear, to me at least.) I'm getting a headache looking through all the alternate functions on all the pins of our chip; such is tech life....

One interesting thing listed is the budgetary price for these chips in quantity 1000, $2.58 each. I'm still amazed how bang per buck continues to increase.

Thanks again for the links to the other documents; I really appreciate it!

The datasheet lists all major features of the IC -- this datasheet covers different variations on the part -- different memory sizes, different packages, and different operating temperature ranges etc. on the attached front page, teh RTC and CRC are listed -- these are on all versions.

228