System Integration Unit (SIU)MPC5566 Microcontroller Reference Manual, Rev. 26-120 Freescale Semiconductor6.4.1.1 Boot ConfigurationThe BOOTCFG[0:1] pins determine the boot mode initiated by the BAM program, and whether externalarbitration is selected for external booting. The BAM program uses the BOOTCFG[0] to determine whereto read the reset configuration halfword (RCHW), and whether to initiate a FlexCAN or eSCI boot.Table 6-155 defines the boot modes specified by the BOOTCFG[0:1] pins. If the RSTCFG pin is assertedduring the assertion of RSTOUT, except in the case of a software external reset, the BOOTCFG pins arelatched four clock cycles prior to the negation of the RSTOUT pin and are used to update the SIU_RSRand the BAM boot mode. Otherwise, if RSTCFG is negated during the assertion of RSTOUT, theBOOTCFG pins are ignored and the boot mode defaults to ‘Boot from internal flash memory.’Refer to Section 16.3.2.2.5, “Read the Reset Configuration Halfword,” for details on the RCHW.6.4.1.2 Pad ConfigurationThe pad configuration registers (SIU_PCR) in the SIU allow software control over the following electricalcharacteristics of the external pads:• Weak pullup/down enable/disable• Weak pullup/down selection• Slew-rate selection for outputs• Drive strength selection for outputs• Input buffer enable (when direction is configured for output)• Input hysteresis enable/disable• Open drain/push-pull output selection• Multiplexed function selection• Data direction selectionThe pad configuration registers are provided to allow centralized control over external pins that are sharedby more than one module. Each pad configuration register controls a single pin.Table 6-155. BOOTCFG[0:1] ConfigurationValue Meaning0b00 Boot from internal flash memory0b01 FlexCAN/eSCI boot0b10 Boot from external memory (no arbitration)0b11 Boot from external memory (external arbitration)
