On Sat, 1 Feb 2014, Jeff Mitchell wrote:
# I need to look up details .. But iirc the f405 haz 192k se as f429
# disco; isn't it 112K main sram, maybe 16Kb sram2 and 64Kb ccm? Maybe ccm
# is counted separate .. If there is another 64KB on a different bus to
# main sram1 I might be in luck. My framebuffer is around 64K.
Finally got a moment to myself; the datasheet for F405 (which I
have 5 of lieing around to use) notes:
"Up to 192+4 Kbytes of SRAM including 64- Kbyte of CCM (core coupled
memory) data RAMUp to 192+4 Kbytes of SRAM including 64- Kbyte of CCM
(core coupled memory) data RAM"
Which is to say, SRAM 112K, SRAM 16K, and CCM 64K. There is no
SRAM3 on the F405.
The F429 looks like they have 256K, so they have an SRAM3 that is
64K. The smallest pincount variation is the LQFP100. I've been trying to
stick with LQFP64 (which is why I went with F405 for now), since it is
much easier to work with in the hobbyist domain. (Not easy to work with,
just easier than 100 pins; a steady hand can still solder it .. most
people don't have a hot air rework station on tap; 100 pins is pretty
tough to hand solder right I find..)
--> but I'll keep it in mind; that extra 64KB SRAM could be the
winner.. stick the main screen framebuffer there, and the offscreen in
CCM, with main ram just being for communications with other chips; if
that'd work without bus contention .. sold!
Theres other options, if I just can't make it work; doing a lot
during hsync is possible; using serial UARTs to a Z180 (instead of Z80, or
a Z80 with a SIO peripheral chip added) might do it, but most serial is
pretty slow.. though Z180 claims it can do 512Kbit which is pretty
impressive. I'd really prefer if I coudl free up up so I could do GPIO
and some SRAM in the STM32 video handler, since then it could just sit on
the Z80 RAM, or at least on the Z80 bus, without resorting to really goofy
tricks (or adding another micro in as an I/O handler that intermediates.)
Anyway, I bore you :)
jeff
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