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P4080 Development System User’s Guide, Rev. 0
40
Freescale Semiconductor
Configuration
6
Configuration
The configuration options are categorized by the following:
•
Requiring software configuration to support evaluation
•
Expected to be easily and often changed by the end-user/developer
•
Should rarely or never be changed
The first two options are implemented with “DIP switches” and/or software-settable options, while the
latter set are usually implemented by resistors that must be added or removed by competent technicians.
This figure shows the configuration logic for those signals configured using switches.
Figure 25. Configuration Logic
The default action is for the ngPIXIS to transfer the switch setting to the processor configuration pin during
the HRESET assertion interval.
In addition, software running on the P4080 can initialize internal registers (such as SWx and ENx) to allow
a board to configure itself for the next restart (termed “self-shmoo” or “self-characterization”).
A third option allows the ngPIXIS to copy configuration data from an external I
2
C EEPROM upon reset,
and apply those values to the SWx/ENx registers (ignoring the external hardware switches). This allows
dispensing with the expensive DIP switches and their corresponding difficulties with set-up and
configuration preservation.
RESET_REQ_B External CPU requests reset
Full reset
tgtrst_b
Internal
Reset request from OCM software
Causes full reset always
rstall
Internal
PX_RST register write
Full reset
go
Internal
ngPIXIS shmoo logic restart request
Causes full reset except:
PX_AUX registers are not changed.
wdtrst_b
Internal
Watchdog timer expired
Causes full restart including shmoo changes, if any
Table 17. Reset Terms (continued)
Term
Type
Description
Notes
P4080
CONFIG_PIN
ngPIXIS
ENx.y
SWx.y
where needed
OVDD
CFGDRV
SW1
EN1
SW2
EN2
...
EEPROM