Serial Channel B Configuration - Digi NS9750 Hardware Reference Manual

Single chip 0.13μm cmos network-attached processor

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Calculation and example

This equation calculates the amount of time, in seconds, required to copy the

contents of the SPI-EEPROM to external memory:

Time = (1 / freq) * EEPROM

SPI master clock frequency = 1.5 MHz

SPI-EEPROM = 256 Kb

Time for operation to complete = 175 ms

Serial Channel B configuration

When exiting the power-on reset state, serial channel B is in SPI master mode, which

facilitates communication with the external SPI-EEPROM. When the copy operation is

complete, serial channel B is returned to its default reset state. The next table shows

which configuration fields are updated by hardware, allowing the SPI master

interface to operate.

Table 292: SPI master mode boot configuration

Enable the channel

8 data bits per word

Chip select polarity to active low

SPI master mode

Bit order to MSB first

Enable the bit rate generator

Synchronous timing

Select BBus clock as reference

Transmit clock inverted

Create ~1.5 MHz SPI clock

w w w . d i g i e m b e d d e d . c o m

B B u s B r i d g e

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