Data Word Formats
9-40
ADSP-2126x SHARC Processor Hardware Reference
Do not set the
SLEN
value to 0 or 1. Words smaller than 32 bits are
right-justified in the receive and transmit buffers, residing in the least sig-
nificant (LSB) bit positions.
Although serial ports process word lengths of 3 to 32 bits, transmitting or
receiving words smaller than 7 bits at one-quarter the full clock rate of the
processor may cause incorrect operation when DMA chaining is enabled.
Chaining disables the processor’s internal I/O bus for several cycles while
the new transfer control block (TCB) parameters are being loaded.
Receive data may be lost (for example, overwritten) during this period.
Transmitting or receiving words smaller than five bits may cause incorrect
operation when all the DMA channels are enabled with no DMA
chaining.
Endian Format
Endian format determines whether serial words transmit MSB-first or
LSB-first. Endian format is selected by the
LSBF
bit in the
SPCTLx
Control
registers. When
LSBF
= 0, serial words transmit (or receive) MSB-first.
When
LSBF
= 1, serial words transmit (or receive) LSB-first.
Data Packing and Unpacking
Received data words of 16 bits or less may be packed into 32-bit words,
and 32-bit words being transmitted may be unpacked into 16-bit words.
Word packing and unpacking is selected by the
PACK
bit in the
SPCTLx
control registers.
When
PACK
= 1 in the Control register, two successive words received are
packed into a single 32-bit word, and each 32-bit word is unpacked and
transmitted as two 16-bit words.
The first 16-bit (or smaller) word is right-justified in bits 15–0 of the
packed word, and the second 16-bit (or smaller) word is right-justified in
bits 31–16. This applies to both receive (packing) and transmit
Содержание ADSP-21261 SHARC
Страница 30: ...Contents xxx ADSP 2126x SHARC Processor Hardware Reference ...
Страница 40: ...Register Diagram Conventions xl ADSP 2126x SHARC Processor Hardware Reference ...
Страница 58: ...Differences From Previous SHARCs 1 18 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 112: ...Secondary Processing Element PEy 2 54 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 178: ...Summary 3 66 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 204: ...DAG Instruction Summary 4 26 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 322: ...Setting Up DMA 7 32 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 436: ...SPORT Programming Examples 9 86 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 521: ...ADSP 2126x SHARC Processor Hardware Reference 11 31 Input Data Port rts IDP_ISR end ...
Страница 522: ...Input Data Port Programming Example 11 32 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 590: ...Timer Programming Examples 14 20 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 796: ...I O Processor Registers A 174 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 800: ...B 4 ADSP 2126x SHARC Processor Core Manual ...
Страница 846: ...Index I 36 ADSP 2126x SHARC Processor Hardware Reference ...