405EX Datasheet, PDF (65/67 Pages) Applied Micro Circuits Corporation – PowerPC 405EX Embedded Processor

PPC405EX – PowerPC 405EX Embedded Processor
Revision 1.09 - August 21, 2007
Preliminary Data Sheet
Initialization
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 in order to enable default
initial conditions before PPC405EX start-up. The actual instant of capture 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 only used for strap functions 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 25. Strapping Pin Assignments
Pin Strapping
Initialization Source
Option
F04
(UART0DCD)
F02
(UART0DSR)
G02
(UART0CTS)
EBC 8-bit wide ROM
A
0
0
0
EBC 16-bit wide ROM
B
0
0
1
EBC 16-bit wide ROM
C
0
1
0
EBC 8-bit wide NAND Flash
D
0
1
1
EBC 8-bit wide NAND Flash
E
1
0
0
IIC ROM at address 0xA8
G
1
0
1
EBC 8-bit wide ROM
F
1
1
0
IIC ROM at address 0xA4
H
1
1
1
Note: See the PPC405EX Embedded Processor User’s Manual for option descriptions and other details regarding the boot process.
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