Digi NS9750 User Manual
Page 509
w w w . d i g i e m b e d d e d . c o m
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B B u s B r i d g e
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
SIZE
Example
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.
Register
Field
Value
Description
Control A
CE
0x1
Enable the channel
Control A
WLS
0x3
8 data bits per word
Control B
CSPOL
0x0
Chip select polarity to active low
Control B
MODE
0x2
SPI master mode
Control B
BITORDR
0x1
Bit order to MSB first
Bit rate
EBIT
0x1
Enable the bit rate generator
Bit rate
TMODE
0x1
Synchronous timing
Bit rate
CLKMUX
0x1
Select BBus clock as reference
Bit rate
TXCINV
0x1
Transmit clock inverted
Bit rate
N
0x00F
Create ~1.5 MHz SPI clock
Table 292: SPI master mode boot configuration