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S E R I A L C O N T R O L M O D U L E : H D L C
DPLL operation: Adjustment ranges and output clocks
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DPLL-tracked bit
cell boundaries
The DPLL counter normally counts by 16 but if a transition occurs earlier or later than
expected, the count is modified during the next count cycle.
If the transition occurs earlier than expected, the bit cell boundaries are early
with respect to the DPLL-tracked cell boundaries and the count is shortened by
either one or two counts.
If the transition occurs later than expected, the bit cell boundaries are late
with respect to the DPLL-tracked bit cell boundaries and the count is
lengthened by either one or two counts.
How far off the DPLL-tracked bit cell boundaries are determines whether the count
is adjusted by one or two. This tracking allows for minor differences in the transmit
and receive clock frequencies.
NRZ and NRZI
data encoding
With NRZ and NRZI data encoding, the DPLL counter runs continuously and adjusts
after every receive data transition.
Because NRZ encoding does not guarantee a minimum density of transitions, the
difference between the sending data rate and the DPLL output clock rate must be
very small, and depends on the longest possible run of zeros in the received frame.
NRZI encoding guarantees at least one transition every six bits (with the inserted
zeroes). Because the DPLL can adjust by two counts every bit cell, the maximum
difference between the sending data rate and the DPLL output clock rate is 1/48
(~2%).
Biphase data
encoding
With biphase data encoding, the DPLL works in multiple-access conditions where
there may not be flags on the idle line. The DPLL properly generates an output clock
based on the first transition in the leading zero of an opening flag. Similarly, the DPLL
requires only the completion of the closing flag to provide the extra two clocks to the
receiver to properly assemble the data.
In biphase-level mode, this means the transition that defines the last zero of
the closing flag.
In the biphase-mark and biphase-space modes, this means the transition that
defines the end of the last zero of the closing flag.
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D P L L o p e r a t i o n : A d j u s t m e n t r a n g e s a n d o u t p u t c l o c k s
This figure shows the adjustment ranges and output clock for the different DPLL
modes of operation:
Содержание NS9215
Страница 1: ...NS9215 Hardware Reference 90000847_C Release date 10 April 2008...
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Страница 26: ...26 Hardware Reference NS9215...
Страница 44: ...P I N O U T 26 5 System clock 44 Hardware Reference NS9215 System clock drawing...
Страница 52: ...P I N O U T 26 5 Power and ground 52 Hardware Reference NS9215...
Страница 80: ...I O C O N T ROL M O D U L E Memory Bus Configuration register 80 Hardware Reference NS9215...
Страница 136: ...WOR KI N G W I TH T H E C P U Noncachable instruction fetches 136 Hardware Reference NS9215...
Страница 202: ...S Y S T E M C O N T RO L M OD U L E RTC Module Control register 202 Hardware Reference NS9215...
Страница 260: ...M E MO R Y C O N T ROL L E R StaticMemory Turn Round Delay 0 3 registers 260 Hardware Reference NS9215...
Страница 354: ...E X T E R N A L D M A DMA Peripheral Chip Select register 354 Hardware Reference NS9215...
Страница 362: ...A E S D AT A E N C R Y P T I O N D E C R Y P T I O N M O D U L E CCM mode 362 Hardware Reference NS9215...
Страница 384: ...I O HU B M OD UL E Module Direct Mode TX Data Last FIFO 384 Hardware Reference NS9215 31 March 2008...
Страница 414: ...S E R I A L C ON T RO L M O D U L E U ART UART Modem Status register 414 Hardware Reference NS9215...
Страница 446: ...S E R I A L C ON T RO L M O D U L E S PI SPI timing characteristics 446 Hardware Reference NS9215...
Страница 472: ...R E A L TI M E C L O C K M O D U L E General Status register 472 Hardware Reference NS9215...
Страница 512: ...TI M I NG Clock timing 512 Hardware Reference NS9215...
Страница 514: ...PA CKA GING Processor Dimensions 514 Hardware Reference NS9215 P r o c e s s o r D i m e n s i o n s...
Страница 515: ...PA CKA GING Processor Dimensions www digiembedded com 515...
Страница 516: ...PA CKA GING Processor Dimensions 516 Hardware Reference NS9215...