SPI master loopback operation, although not included in the M68HC11 reference manual, has been implemented to expedite testing. This operation is selected by setting the loopback bit in the SPICR (SPICR(0)) enabling an internal connection from the transmitter output to the receiver input. The receiver and transmitter operate normally, except that received data (from a remote slave) is ignored. This operation is relevant only when the SPI device is configured as a master and operated in standard SPI transaction mode. When the core is configured in dual or quad SPI mode, loopback mode is not supported.