From 702e6014f15b307f144fa03ecaf83a8446c6802a Mon Sep 17 00:00:00 2001 From: Wolfgang Denk Date: Sun, 29 Apr 2012 23:57:39 +0000 Subject: doc: cleanup - move board READMEs into respective board directories Also drop a few files referring to no longer / not yet supported boards. Signed-off-by: Wolfgang Denk Cc: Prafulla Wadaskar Cc: Stefan Roese Cc: Kim Phillips Cc: Andy Fleming Cc: Jason Jin Cc: Stefano Babic Cc: Daniel Schwierzeck Acked-by: Stefano Babic Acked-by: Daniel Schwierzeck --- doc/README.MBX | 68 ---------------------------------------------------------- 1 file changed, 68 deletions(-) delete mode 100644 doc/README.MBX (limited to 'doc/README.MBX') diff --git a/doc/README.MBX b/doc/README.MBX deleted file mode 100644 index c889fe9791..0000000000 --- a/doc/README.MBX +++ /dev/null @@ -1,68 +0,0 @@ -IMPORTANT NOTE - read before defining CONFIG_SYS_USE_OSCCLK in your board - config file!!! - - -WARNING: Wrong settings of this parameter have the potential to -damage hardware by running the MBX's CPU at frequencies that exceed -it's rating and/or overdriving the it's SPLL! - - -Ramblings: -1) Motorola offered 12 different variants of the MBX, 6 823s and 6 860s. -2) Of these 12 variants, only 2 were entry level boards. -3) I believe that the 2 entry level boards were the only ones that - used OSCM clocking. I can't be completely certain of this at this - point. -4) Motorola never offered an MBX that ran faster than 50Mhz. -5) The 10, non-entry level boards, ran at 40Mhz. -6) The EXTCLK input has a minimum clock of 15Mhz for the 823/860. -7) Motorola no longer sells MBXs. - -Based on this information, I can surmise that the default power-on -reset clocking was one of the following three options. - -Multiplier SPLL Options ------------------------------------- -513 OSCM is SPLL input -5 OSCM is SPLL input -1 EXTCLK is SPLL input - -The forth option: - -5 EXTCLK is SPLL input - -is not possible on MBXs. This is because the minimum EXTCLK input -frequency is 15Mhz. 5 * 15Mhz = 75 Mhz. There was no variant that ran -above 50 Mhz. - -The board I have borrowed definitely uses a multiplier of 1 for -EXTCLK and runs at 40Mhz. I even went so far as to put a scope on it. - -One of the two default OSCM modes are most likely what was used on -the entry level boards to cheapen them by eliminating the external -crystal oscillator. - -To add insult to injury, the stupid 860 PLPRCR register retains it's -multiplication factor through hard resets. You can't clear it out -because it is battery backed and once it is set wrong, it stays -wrong. The only way to reset it, so that it takes on it's default -multiplier is to disconnect all power including external, batteries, -as well discharging caps on the board. This precludes the fact that -your 860 may be quite DEAD by this time! - -If you don't setup the multiplication factor for boards that use the -OSCM input, they won't run correctly, but at least they won't be -dead. - -Addtionally, there is no good way to determine the clock input source -from CPU register data. The only way to deal with this is either hard -code it, determine the correct value with some rather NASTY timing -loops, or try to grok it from external data sources. Motorola -firmware opts for the NASTY timing loops, but needs to configure the -serial ports to do so. - - -You may have a legitimate need to define CONFIG_SYS_USE_OSCCLK if your -MBX8xx board is using the OSCM clocking mode. - -You better know what you are doing here. -- cgit v1.2.1