My Freescale TWR-MPC5125 board instantly reboots if I touch any physical address on the LocalPlus Bus (LPB) with disabled NFC clock.
I've reproduced TWR-MPC5125 simply in uboot.
This is the annotated procedure:
=> md.l 0x80000e10 /* Reset Status Register */
80000e10: 60000000 /* All flags are cleared (just powered on) */
=> md.l 0x80000f04 /* System Clock Control Register 1 */
80000f04: e404b600 /* NFC clock is enabled */
=> md.l 0xfff00000 /* Reading from MRAM living at LPB CS0 */
fff00000: cafea134 /* Works fine */
=> mw.l 0x80000f04 0xc404b600 1 /* Disable NFC clock */
=> md.l 0x80000f04
80000f04: c404b600 /* NFC clock is disabled now */
=> md.l 0xfff00000 /* Reading from MRAM again */
/* The board has just suddenly reset. Uboot is restarting. */
U-Boot 2009.03-00004-gd37ab38 (Apr 14 2010 - 10:48:22) MPC512X
CPU: MPC5125 rev. 1.0, Core e300c4 at 393.216 MHz, CSB at 196.608 MHz
=> md.l 0x80000e10 /* Read RSR */
80000e10: 60000040 /* Only external HRESET1 event has occurred */
Rising of EXT1HRS flag is not special for this crash.
EXT1HRS is similarly set if I execute 'reset' command in uboot
or call 'reboot' from Linux.
Did I find some new errata?