CrossLink Programming and Configuration Usage Guide
Technical Note
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FPGA-TN-02014-1.2
6.1.
Configuration Mode and Port Options
The configuration and port options allow you to set which configuration ports continue to operate after the CrossLink
device enters User Mode. You can also control the availability of status pins, as well as the speed at which configuration
data is read from an external PROM. The selections made here are saved in the Feature Row and remain in effect until
the Feature Row is erased. The only exception is the MCCLK_FREQ parameter, which is stored in the configuration data.
The configuration and port options can be used in any combination.
Table 6.1. Configuration Mode/Port Options
Option Name
Default Setting
All Settings
SLAVE_SPI_PORT
ENABLE
DISABLE, ENABLE
MASTER_SPI_PORT
DISABLE
DISABLE, ENABLE
I2C_PORT
DISABLE
DISABLE, ENABLE
MCCLK_FREQ
2
See description below
TRANSFR
OFF
OFF,ON
CDONE_PORT
CDONE_USER_IO
CDONE_ONLY, CDONE_USER_IO
Slave SPI Port
The SLAVE SPI_PORT allows you to preserve the Slave SPI configuration port after the CrossLink device enters User
Mode. The SLAVE_SPI_PORT preference can be set in two states:
ENABLE
— This setting preserves the Slave SPI port I/O when the CrossLink device is in User Mode. When the pins
are preserved, an external SPI master controller can interact with the Configuration Logic. Choosing ENABLE also
prevents you from over-assigning I/O to the port pins.
DISABLE
— This setting disconnects the SPI port pins from the Configuration Logic. By itself it does not make the
port pins general purpose I/O. Both SLAVE_SPI_PORT and MASTER_SPI_PORT must be set to disable to make the
port pins general purpose I/O.
Master SPI Port
The MASTER SPI_PORT allows you to preserve the Master SPI configuration port after the CrossLink device enters User
Mode. The MASTER_SPI_PORT preference can be set in two states:
ENABLE
— This setting preserves the Master SPI port I/O when the CrossLink device is in User Mode. Choosing
ENABLE also prevents you from over-assigning I/O to the port pins.
DISABLE
— This setting disconnects the SPI port pins from the Configuration Logic. By itself it does not make the
port pins general purpose I/O. Both SLAVE_SPI_PORT and MASTER_SPI_PORT must be set to disable to make the
port pins general purpose I/O.
I
2
C Port
The I2C_PORT allows you to preserve the I
2
C configuration port after the CrossLink device enters User Mode. The
I2C_PORT preference can be set in two states:
ENABLE
— This setting preserves the I
2
C port I/O when the CrossLink device is in User Mode. Choosing ENABLE
also prevents
you from over-assigning I/O to the port pins.
DISABLE
— This setting disconnects the I
2
C port pins from the Configuration Logic. The port pins become general
purpose I/O.
MCCLK Frequency
The MCCLK_FREQ preference allows you to alter the MCCLK frequency used to retrieve data from an external SPI Flash
when using EXTERNAL or Dual Boot configuration modes. The MCCLK_FREQ value is stored in the incoming
configuration data. It is not stored in the Feature Row. The CrossLink device reads a series of padding bits, a “start of
data” word (0xBDB3) and a control register value. The control register contains the new MCCLK_FREQ value. CrossLink
switches to the new clock frequency shortly after receiving the MCCLK_FREQ value.
