P2 Taqoz V2.8 for 25MHz Crystal of Kiss with SD-Card @921600 baud
So, if you want to run P2 Taqoz V2.8 for 25MHz Crystal of Kiss board with SD-Card @921600 baud:
To be aligned with Bobs great docu https://forums.parallax.com/discussion/173302/taqoz-reloaded-v2-8-word-glossary/p1
this is for V2.8 which is found https://sourceforge.net/projects/tachyon-forth/files/TAQOZ/binaries/ Taqoz.zip
Included is the original ZIP of V2.8 and also a ZIP, which contains a patched bootfile for 25MHz crystal.
Patching was done with the following steps:
R4 pulldown removed. Original bootfile _BOOT_P2.BIX copied to a sd card.
Due to the 25MHz cristal, the clock frequency is 250MHz instead of 200MHz and baud rate is 1152000 ( = 921600 *25/20 ) .
Terminal program PuTTY can switch a prop plug to this unusual baudrate. Now you can contact Taqoz on P2. :-)
There is in the DAT section of the source "taqoz.spin2":
XIDIV = 1 ' crystal/osc input divider'
VCODIV = 1
CLKMUL = CPUHZ/(XIN/XIDIV)
CLKCFG = 1<<24+(XIDIV-1)<<18+(CLKMUL-1)<<8+((VCODIV-2)&$0F)<<4+PF15
Original value of CLKCFG is : $0100_09F8
This constant is located at 24decimal.
To get a system running at 200 MHz with crystal 25MHz and with baud rate 921600:
$0100_07F8 24 !
200.000.000 20 !
25.000.000 16 !
After booting the baud rate is 921600 as intended and the clock frequency is 200MHz.