NXP Semiconductors MPC5566, Reference Manual

Page: 183 / 1268

Reset
MPC5566 Microcontroller Reference Manual, Rev. 2
4-14 Freescale Semiconductor
The following table describes the fields in the reset configuration halfword:
Table 4-8. Internal Boot RCHW Field Descriptions
Field Description
0–4 Reserved: These bit values are ignored when the halfword is read. Write to 0 for future compatibility.
5
WTE
Watchdog timer enable.
This is used to enable or disable the e200z6 watchdog timer through the BAM program. The configuration of
the watchdog timer function is managed through the timer control register (TCR).
0 BAM does not write the e200z6 timebase registers (TBU and TBL) nor enable the e200z6 core watchdog
timer.
1 BAM writes the e200z6 timebase registers (TBU and TBL) to 0x0000_0000_0000_0000 and enables the
e200z6 core watchdog timer with a time-out period of 3 x 2
17
system clock cycles.
(Example: For 8 MHz crystal
−>
12MHz system clock
−>
32.7mS time-out.
For 20 MHz crystal
−>
30 MHz system clock
−>
13.1mS time-out)
6
PS0
Port size.
Defines the width of the data bus connected to the memory on CS[0]. After system reset, CS[0] is changed to
a 16-bit port by the BAM which fetches the RCHW from either 16- or 32-bit external memories. Then the BAM
reconfigures the EBI either as a 16-bit bus or a 32-bit bus, according to the settings of this bit.
0 32-bit CS[0] port size
1 16-bit CS[0] port size
Note: Used only in external boot mode. Do not set the port to 32-bits if the device only has a 16-bit data bus.
7
VLE
VLE Code Indicator.
This bit is used to configure the MMU for the boot block to execute as either Classic Power Architecture Book
E code or as Freescale VLE code.
0 = Boot code executes as Classic Power Architecture Book E code
1 = Boot code executes as Freescale VLE code
8–15
BOOTID[0:7]
Boot identifier.
This field serves two functions. First, it is used to indicate which block in flash memory contains the boot
program. Second, it identifies whether the flash memory is programmed or invalid. The value of a valid boot
identifier is 0x5A (0b01011010). The BAM program checks the first halfword of each flash memory block
starting at block 0 until a valid boot identifier is found. If all blocks in the low address space of the internal flash
are checked and no valid boot identifier is found, then the internal flash is assumed to be invalid and a CAN/SCI
boot is initiated. For an external boot, only block 0 is checked for a valid boot identifier, and if not found, a
CAN/SCI boot is initiated.