Both the DPU and eSC provide status indications once code has been downloaded and self
tests have been run to verify functionality of each on board processor. The dpu_gpio[7]/
DPU Status and esc_gpio[7]/eSC Status pins can be optionally used to provide an
indication of the status for each processor. However, these status pins toggle regularly
during normal operation. Both the dpu_gpio[7] and esc_gpio[7] pins are active high
outputs when used to indicate status and can be connected to drive an LED as an indicator.
If the eSC is not used for running on-chip IKE or other eSC-based code, then the eSC
Status pin is not required.
Flash Interface (Optional)
The Serial Flash Interface via the Serial Peripheral Interface is supported on esc_gpio[4:0]
as a primary function. The esc_gpio[4:0] pins are programmed to function as the Flash
device interface when the boot_config_1 pin is asserted high and will become active when
the chip is booting. They can be reclaimed later and used for “general purpose’ pins in a
system in a system that does not use Flash, however they will again revert to their Flash
functionality when the chip re-boots after a hard reset or power cycle.
Note
Note that a Flash may be connected, but only used for Persistent Storage and not for
bootload. In this case, the boot_config_1 pin state need not be asserted high.
Hifn provides code to emulate the Serial Peripheral Interface (SPI) type serial Flash device
bus with capacities from 128KBytes to 32MBytes on the esc_gpio[4:0] pins.
MDIO Signaling (Optional)
The MDIO signalling for PHY management may optionally be supported on dpu_gpio[5]
and dpu_gpio[6] to function as the MDC and MDIO respectively. Only the “initiator” side of
the MDIO function is supported, therefore the 4450 expects to be initiating communications
with PHY devices. This interface does NOT support receiving MDIO queries from another
MDIO master (such as a MAC device). Hifn provides Station Management Software (STM)
to support this function. Since the STM software runs on the eSC, the external SDRAM must
be populated in order to use the MDIO signalling.
In addition, for SFP applications, I2C signalling may optionally be supported on
dpu_gpio[5] and dpu_gpio[6] to function as the SCL and SDA respectively. The STM
software running on the eSC processor can configure the SFP and query its internal EEPROM
via this interface.
Device ID
In applications requiring multiple 4450s, esc_gpio[6:4] may be used to set a device ID.
The device_id[2:0] pins (esc_gpio[6:4]) are sampled and latched at reset and can be
reclaimed for alternate uses for user defined functionality in normal operation. The Device
ID pins should be tied high or low through separate resistors to allow for reuse during
normal operation.
RGMI/RTBI Voltage Select
4450 – Data Sheet, DS-0131-06
Page59
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