Microchip Technology MA300015 Data Sheet

© 2011 Microchip Technology Inc.

DS70150E-page 109

The module supports a basic framed SPI protocol in
Master or Slave mode. The control bit, FRMEN,
enables framed SPI support and causes the SSx pin to
perform the Frame Synchronization pulse (FSYNC)
function. The control bit SPIFSD determines whether
the SSx pin is an input or an output (i.e., whether the
module receives or generates the Frame Synchroniza-
tion pulse). The frame pulse is an active-high pulse for
a single SPI clock cycle. When Frame Synchronization
is enabled, the data transmission starts only on the
subsequent transmit edge of the SPI clock.

The SSx pin allows a Synchronous Slave mode. The
SPI must be configured in SPI Slave mode, with SSx
pin control enabled (SSEN = 1). When the SSx pin is
low, transmission and reception are enabled, and the
SDOx pin is driven. When SSx pin goes high, the SDOx
pin is no longer driven. Also, the SPI module is re-
synchronized, and all counters/control circuitry are
reset. Therefore, when the SSx pin is asserted low
again, transmission/reception will begin at the MSb,
even if SSx had been de-asserted in the middle of a
transmit/receive.

During Sleep mode, the SPI module is shut down. If
the CPU enters Sleep mode while an SPI transaction
is in progress, then the transmission and reception is
aborted.

The transmitter and receiver will stop in Sleep mode.
However, register contents are not affected by
entering or exiting Sleep mode.

When the device enters Idle mode, all clock sources
remain functional. The SPISIDL bit (SPIxSTAT<13>)
selects if the SPI module will stop or continue on Idle.
If SPISIDL = 0, the module will continue to operate
when the CPU enters Idle mode. If SPISIDL = 1, the
module will stop when the CPU enters Idle mode.