ADSP-BF537 Blackfin Processor Hardware Reference
12-27
SPORT Controllers
When an internal frame sync is selected (
ITFS
=
1
in the
SPORTx_TCR1
reg-
ister or
IRFS
=
1
in the
SPORTx_RCR1
register) and frame syncs are not
required, the first frame sync does not update the clock divider if the value
in
SPORTx_TCLKDIV
or
SPORTx_RCLKDIV
has changed. The second frame
sync will cause the update.
The
SPORTx_TFSDIV
and
SPORTx_RFSDIV
registers specify the number of
transmit or receive clock cycles that are counted before generating a
TFS
or
RFS
pulse (when the frame sync is internally generated). This enables a
frame sync to initiate periodic transfers. The counting of serial clock
cycles applies to either internally or externally generated serial clocks.
The formula for the number of cycles between frame sync pulses is:
# of transmit serial clocks between frame sync assertions =
1
# of receive serial clocks between frame sync assertions =
1
Use the following equations to determine the correct value of
TFSDIV
or
RFSDIV
, given the serial clock frequency and desired frame sync frequency:
SPORTxTFS frequency = (TSCLKx frequency)/(SPORTx_ 1
)
SPORTxRFS frequency = (RSCLKx frequency)/(SPORTx_ 1
)
The frame sync would thus be continuously active (for transmit if
TFSDIV = 0
or for receive if
RFSDIV = 0
). However, the value of
TFSDIV
(or
RFSDIV
) should not be less than the serial word length minus 1 (the
value of the
SLEN
field in
SPORTx_TCR2
or
SPORTx_RCR2
). A smaller value
could cause an external device to abort the current operation or have other
unpredictable results. If a SPORT is not being used, the
TFSDIV
(or
RFS-
DIV
) divisor can be used as a counter for dividing an external clock or for
generating a periodic pulse or periodic interrupt. The SPORT must be
enabled for this mode of operation to work.
Summary of Contents for Blackfin ADSP-BF537
Page 42: ...Contents xlii ADSP BF537 Blackfin Processor Hardware Reference ...
Page 90: ...Development Tools 1 32 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 138: ...Programming Examples 4 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 340: ...SDC Programming Examples 6 84 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 606: ...Programming Examples 9 94 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 660: ...Programming Examples 10 54 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 720: ...Electrical Specifications 11 60 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 840: ...Programming Examples 13 42 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 876: ...Programming Examples 14 36 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 938: ...Programming Examples 15 62 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 958: ...Programming Examples 17 12 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 986: ...Programming Examples 18 28 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 1162: ...G 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 1218: ...Index I 56 ADSP BF537 Blackfin Processor Hardware Reference ...