Revision 1.07 – September 10, 2007
PPC405EP – PowerPC 405EP Embedded Processor
Initialization
Data Sheet
The following describes the method by which initial chip settings are established when a system reset occurs.
Strapping
When the SysReset input is driven low (system reset), the state of certain I/O pins is read to enable default initial
conditions prior to PPC405EP start-up. The actual capture instant is the nearest system clock edge before the
deassertion of reset. These pins must be strapped using external pull-up (logical 1) or pull-down (logical 0)
resistors to select the desired default conditions. The recommended pull-up is 3kΩ to +3.3V or 10kΩ to +5V. The
recommended pull-down is 1KΩ to GND. These pins are use for strap functions only during reset. They are used
for other signals during normal operation. The following table lists the strapping pins along with their functions and
strapping options. The signal names assigned to the pins for normal operation appear below the pin number.
Table 16. Strapping Pin Assignments
Function
Option
Ball Strapping
P04
IIC EEPROM controller
UART0_Tx
If the controller is enabled, 32 bytes of configuration data
are read from the EEPROM.
Disable
Enable
0
1
EEPROM address (P04 = 1)
or
Boot ROM width (P04 = 0)
N02
UART0_RTS
Y17
SysErr
When P04 = 1, these pins set the high-order two
bits of the EEPROM base address.
High order EEPROM base address bits
Address bit
Address bit
8 bits
0
0
1
1
0
1
0
1
When P04 = 0, these pins indicated the width of
the boot ROM.
16 bits
reserved
reserved
EEPROM
During reset, configuration values other than the internal default values can be read from a serial EEPROM
connected to the IIC port. The association of bits in the EEPROM with the configuration values and their default
values are covered in detail in the PowerPC 405EP Embedded Processor User’s Manual.
Note: If P04 is strapped to 1, and the EEPROM is not connected or is defective, the PPC405EP remains in the
reset state and will not boot.
48
AMCC
AMCC [ APPLIED MICRO CIRCUITS CORPORATION ]
