Control Center Serial

SPI Write Command

<spi_write ss="ss"
           count="count"
           radix="radix">
     message
</spi_write>

Write a stream of bytes to the downstream SPI slave device and read back the full-duplex response.

Parameters

ss

SPI slave select to use for the transaction (0-7).

count

The number of bytes to write (maximum 65535).

radix

The base of the number system of the message, with the value being 10 for decimal, or 16 for hexadecimal.

message

The message to transmit as a space separated list of numbers.

Details

If count is greater than the number of bytes in the message, the remaining bytes are clocked with all bits set to zero. This allows for a shorter representation of read commands.

If count is 0, no bytes will be written to the slave. However, the slave select line will be dropped for 5-10 microseconds. This can be useful in sending a signal to a downstream SPI slave without actually sending any bytes. For example, if an SPI slave has tied the slave select to an interrupt line and it sees the line is toggled without any bytes sent, it can interpret the action as a command to prepare its firmware for an subsequent reception of bytes.

Please see the Aardvark I2C/SPI Adapter User Manual or the Promira Serial Platform User Manual for more information.