
Operation Modes
10-26
ADSP-214xx SHARC Processor Hardware Reference
Clocking Options
In standard serial mode, the serial ports can either accept an external serial
clock or generate it internally. The
ICLK
bit in the
SPCTL
register deter-
mines the selection of these options. For internally-generated serial clocks,
the
CLKDIV
bits in the
DIVx
register configure the serial clock rate.
Finally, programs can select whether the serial clock edge is used for sam-
pling or driving serial data and/or frame syncs. This selection is performed
using the
CKRE
bit in the
SPCTL
register.
Frame Sync Options
This section describes the different options for frame sync in standard
serial mode.
Framed Versus Unframed Frame Syncs
The use of frame sync signals is optional in serial port communications.
The
FSR
(transmit frame sync required) bit determines whether frame sync
signals are required. Active low or active high frame syncs are selected
using the
LFS
bit. This bit is located in the
SPCTLx
control registers.
When
FSR
is set (=1), a frame sync signal is required for every data word.
To allow continuous transmission from the processor, each new data word
must be loaded into the transmit buffer before the previous word is shifted
out and transmitted.
When
FSR
is cleared (=0), the corresponding frame sync signal is not
required. A single frame sync is required to initiate communications but it
is ignored after the first bit is transferred. Data words are then transferred
continuously in what is referred to as an unframed mode.
When DMA is enabled in a mode where frame syncs are not
required, DMA requests may be held off by chaining or may not be
serviced frequently enough to guarantee continuous unframed data
flow.
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Summary of Contents for SHARC ADSP-214 Series
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Page 72: ...Notation Conventions lxxii ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
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Page 264: ...Programming Models 3 134 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
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Page 396: ...Effect Latency 7 28 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
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Page 616: ...Debug Features 14 22 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
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Page 1132: ...Register Listing A 306 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Page 1192: ...Index I 34 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...