Analog Devices ADSP-BF59x Blackfin, Hardware Reference Manual, Page: 536 / 772

Functional Description
14-30 ADSP-BF59x Blackfin Processor Hardware Reference
Frame Sync Options
Framing signals indicate the beginning of each serial word transfer. The
framing signals for each SPORT are
TFS
(transmit frame sync) and
RFS
(receive frame sync). A variety of framing options are available; these
options are configured in the SPORT configuration registers (
SPORT_TCR1
,
SPORT_TCR2
,
SPORT_RCR1
and
SPORT_RCR2
). The
TFS
and
RFS
signals of a
SPORT are independent and are separately configured in the control
registers.
Framed Versus Unframed
The use of multiple frame sync signals is optional in SPORT communica-
tions. The
TFSR
(transmit frame sync required select) and
RFSR
(receive
frame sync required select) control bits determine whether frame sync sig-
nals are required. These bits are located in the
SPORT_TCR1
and
SPORT_RCR1
registers.
When
TFSR
= 1 or
RFSR
= 1, a frame sync signal is required for every data
word. To allow continuous transmitting by the SPORT, each new data
word must be loaded into the
SPORT_TX
hold register before the previous
word is shifted out and transmitted.
When
TFSR
= 0 or
RFSR
= 0, the corresponding frame sync signal is not
required. A single frame sync is needed to initiate communications but is
ignored after the first bit is transferred. Data words are then transferred
continuously, unframed.

With frame syncs not required, interrupt or DMA requests may
not be serviced frequently enough to guarantee continuous
unframed data flow. Monitor status bits or check for a SPORT
Error interrupt to detect underflow or overflow of data.