
S E R I A L C O N T R O L M O D U L E : H D L C
Digital phase-locked-loop (DPLL) operation: Encoding
418
Hardware Reference NS9215
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D i g i t a l p h a s e - l o c k e d - l o o p ( D P L L ) o p e r a t i o n : E n c o d i n g
In the HDLC module, the internal clock comes from the output of the dedicated
divider. The divider output is divided by 16 to form the transmit clock and is fed to
the DPLL to form the receive clock. The DPLL basically is a divide-by-16 counter
that uses the transition timings on the receive data stream to adjust its count. The
DPLL adjusts the count so the DPLL output is placed properly in the bit cells to
sample the receive data.
Transitions
To work properly, the receive data stream requires transitions. NRZ data encoding
does not guarantee transitions in all cases (for example, a long string of zeroes), but
the other data encodings do. NRZI guarantees transitions because of inserted zeroes.
The Biphase encodings all have at least one transition per bit cell.
NRZ Data
HDLC Clock
NRZI
NRZI
Biphase-Level
Biphase-Space
Biphase-Space
Biphase-Mark
Biphase-Mark
data
1
0
1
0
0
1
1
0
Summary of Contents for NS9215
Page 1: ...NS9215 Hardware Reference 90000847_C Release date 10 April 2008...
Page 3: ......
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Page 26: ...26 Hardware Reference NS9215...
Page 44: ...P I N O U T 26 5 System clock 44 Hardware Reference NS9215 System clock drawing...
Page 52: ...P I N O U T 26 5 Power and ground 52 Hardware Reference NS9215...
Page 80: ...I O C O N T ROL M O D U L E Memory Bus Configuration register 80 Hardware Reference NS9215...
Page 136: ...WOR KI N G W I TH T H E C P U Noncachable instruction fetches 136 Hardware Reference NS9215...
Page 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...
Page 354: ...E X T E R N A L D M A DMA Peripheral Chip Select register 354 Hardware Reference NS9215...
Page 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...
Page 512: ...TI M I NG Clock timing 512 Hardware Reference NS9215...
Page 515: ...PA CKA GING Processor Dimensions www digiembedded com 515...
Page 516: ...PA CKA GING Processor Dimensions 516 Hardware Reference NS9215...