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Discussion Groups | 68HC12 | S12D/E pad layout
Join our technical discussions about Freescale Microcontrollers: M68HC12. (Freescale Semiconductor is a Subsidiary of Motorola).
Re: S12D/E pad layout - Edward Karpicz - Jul 18 15:16:44 2007
James M. Knox wrote:
>
> I've used the 912D60A for years. It's time to move up to something
> better - and that appears to be something like the S12D64 or the
> S12E64. [All I really need is reasonable RAM/Flash and SPI
> interface. I like the S12UF with USB, but I lose the SPI.]
E64 doesn't have CAN module; so you probably want A64, not D64. A64 is
cheaper twin of D64, just without MSCAN. Are you using on chip EEPROM? If
not, or if you don't mind using flash to emulate EEPROM, then check also C
and GC families. BTW E and C families can work equally well from 3.3V and
5V supplies and have on chip LVR (low voltage reset) feature, you could save
on supervisor chip. Of course the 9S12XD64/XA64 could be the best probably,
but we need to wait N years before these will be available; and only quite
expensive XDx256/XA256 are available at the moment.
>
> Aside from being cheaper than the D60A, these let me use both
> Colpitts and Pierce forms of oscillator. So I looked at the
> suggested PCB layouts (Freescale Oscillator Block Guide) and frankly,
> I'm not sure it makes sense (please ignore the fact that I *should*
> know these things).
It looks like single layer PCB.
Regards,
Edward
>
> Q1: Are they indeed suggesting a grounded layer immediately under
> the uP IC? [I have a ground plane, but it's a layer or two down.]
>
> Q2: It appears they are creating a star by leaving gaps in that
> ground plane, correct?
>
> Q3: *If* they indeed want a top surface layer to look like that,
> just how the heck do they expect to get to about half the OTHER pins
> on the IC. There isn't even any way to slip a bunch of VIAs in there.
>
> Okay, these should be questions I should know the answer to, but just
> once I would like one of the crystal to work the first time. jmk
>
> -----------------------------------------------
> James M. Knox
> TriSoft ph 512-385-0316
> 1300 Koenig Lane West fax 512-371-5716
> Suite 200
> Austin, Tx 78756 j...@trisoft.com
> -----------------------------------------------
> Yahoo! Groups Links
>
(You need to be a member of 68hc12 -- send a blank email to 68hc12-subscribe@yahoogroups.com )
>
> I've used the 912D60A for years. It's time to move up to something
> better - and that appears to be something like the S12D64 or the
> S12E64. [All I really need is reasonable RAM/Flash and SPI
> interface. I like the S12UF with USB, but I lose the SPI.]
E64 doesn't have CAN module; so you probably want A64, not D64. A64 is
cheaper twin of D64, just without MSCAN. Are you using on chip EEPROM? If
not, or if you don't mind using flash to emulate EEPROM, then check also C
and GC families. BTW E and C families can work equally well from 3.3V and
5V supplies and have on chip LVR (low voltage reset) feature, you could save
on supervisor chip. Of course the 9S12XD64/XA64 could be the best probably,
but we need to wait N years before these will be available; and only quite
expensive XDx256/XA256 are available at the moment.
>
> Aside from being cheaper than the D60A, these let me use both
> Colpitts and Pierce forms of oscillator. So I looked at the
> suggested PCB layouts (Freescale Oscillator Block Guide) and frankly,
> I'm not sure it makes sense (please ignore the fact that I *should*
> know these things).
It looks like single layer PCB.
Regards,
Edward
>
> Q1: Are they indeed suggesting a grounded layer immediately under
> the uP IC? [I have a ground plane, but it's a layer or two down.]
>
> Q2: It appears they are creating a star by leaving gaps in that
> ground plane, correct?
>
> Q3: *If* they indeed want a top surface layer to look like that,
> just how the heck do they expect to get to about half the OTHER pins
> on the IC. There isn't even any way to slip a bunch of VIAs in there.
>
> Okay, these should be questions I should know the answer to, but just
> once I would like one of the crystal to work the first time.
>
> -----------------------------------------------
> James M. Knox
> TriSoft ph 512-385-0316
> 1300 Koenig Lane West fax 512-371-5716
> Suite 200
> Austin, Tx 78756 j...@trisoft.com
> -----------------------------------------------
> Yahoo! Groups Links
>
(You need to be a member of 68hc12 -- send a blank email to 68hc12-subscribe@yahoogroups.com )
Re: S12D/E pad layout - "James M. Knox" - Jul 18 17:02:59 2007
At 21:37 7/18/2007 +0300, you wrote:
> > I've used the 912D60A for years. It's time to move up to something
> > better - and that appears to be something like the S12D64 or the
> > S12E64. [All I really need is reasonable RAM/Flash and SPI
> > interface. I like the S12UF with USB, but I lose the SPI.]
>
>E64 doesn't have CAN module; so you probably want A64, not D64. A64 is
>cheaper twin of D64, just without MSCAN. Are you using on chip EEPROM? If
>not, or if you don't mind using flash to emulate EEPROM, then check also C
>and GC families. BTW E and C families can work equally well from 3.3V and
>5V supplies and have on chip LVR (low voltage reset) feature, you could save
>on supervisor chip. Of course the 9S12XD64/XA64 could be the best probably,
>but we need to wait N years before these will be available; and only quite
>expensive XDx256/XA256 are available at the moment.
No need for CAN on this, or an SCI. Do need an SPI. I am going to
be hooking to a USB, but it looks like a separate USB module may be
the best solution there. [BOM parts cost is not a major driver.]
A very small amount of on-chip EEPROM is useful, but not
necessary. I probably will only need a few bytes of EEPROM, and I
can steal that much from a serial EEPROM somewhere on the board if needed.
Everything is 5 V. and low power is nice but not critical. [A
**big** change from most of the stuff I design.]
Frankly, my selection was made as much as anything by what seemed to
be readily available on the small qty market, in a QFN-80 package.
> > Aside from being cheaper than the D60A, these let me use both
> > Colpitts and Pierce forms of oscillator.
>
>It looks like single layer PCB.
One of the biggest problems I typically have with a D60A is getting
enough space to fan out the pins **and** still keep some semblance of
a layout that will let the oscillator work from a crystal. Last
couple of designs I just said the heck with it and used an external
TTL oscillator. [NEVER had any of these problems with the old 912B32, never!]
Hence the theory that I would go to their reference design for the
S12 and try to emulate their osc. parts locations EXACTLY. But I
sure don't see how they plan to get to half the pins on the part,
even with a 4-layer board.
jmk
-----------------------------------------------
James M. Knox
TriSoft ph 512-385-0316
1300 Koenig Lane West fax 512-371-5716
Suite 200
Austin, Tx 78756 j...@trisoft.com
-----------------------------------------------
(You need to be a member of 68hc12 -- send a blank email to 68hc12-subscribe@yahoogroups.com )
> > I've used the 912D60A for years. It's time to move up to something
> > better - and that appears to be something like the S12D64 or the
> > S12E64. [All I really need is reasonable RAM/Flash and SPI
> > interface. I like the S12UF with USB, but I lose the SPI.]
>
>E64 doesn't have CAN module; so you probably want A64, not D64. A64 is
>cheaper twin of D64, just without MSCAN. Are you using on chip EEPROM? If
>not, or if you don't mind using flash to emulate EEPROM, then check also C
>and GC families. BTW E and C families can work equally well from 3.3V and
>5V supplies and have on chip LVR (low voltage reset) feature, you could save
>on supervisor chip. Of course the 9S12XD64/XA64 could be the best probably,
>but we need to wait N years before these will be available; and only quite
>expensive XDx256/XA256 are available at the moment.
No need for CAN on this, or an SCI. Do need an SPI. I am going to
be hooking to a USB, but it looks like a separate USB module may be
the best solution there. [BOM parts cost is not a major driver.]
A very small amount of on-chip EEPROM is useful, but not
necessary. I probably will only need a few bytes of EEPROM, and I
can steal that much from a serial EEPROM somewhere on the board if needed.
Everything is 5 V. and low power is nice but not critical. [A
**big** change from most of the stuff I design.
Frankly, my selection was made as much as anything by what seemed to
be readily available on the small qty market, in a QFN-80 package.
> > Aside from being cheaper than the D60A, these let me use both
> > Colpitts and Pierce forms of oscillator.
>
>It looks like single layer PCB.
One of the biggest problems I typically have with a D60A is getting
enough space to fan out the pins **and** still keep some semblance of
a layout that will let the oscillator work from a crystal. Last
couple of designs I just said the heck with it and used an external
TTL oscillator. [NEVER had any of these problems with the old 912B32, never!]
Hence the theory that I would go to their reference design for the
S12 and try to emulate their osc. parts locations EXACTLY. But I
sure don't see how they plan to get to half the pins on the part,
even with a 4-layer board.
jmk
-----------------------------------------------
James M. Knox
TriSoft ph 512-385-0316
1300 Koenig Lane West fax 512-371-5716
Suite 200
Austin, Tx 78756 j...@trisoft.com
-----------------------------------------------
(You need to be a member of 68hc12 -- send a blank email to 68hc12-subscribe@yahoogroups.com )