
. . . . .
S E R I A L C O N T R O L M O D U L E : H D L C
Receive and transmit operations
www.digiembedded.com
415
Serial Control Module: HDLC
C
H
A
P
T
E
R
1
1
T
he HDLC module allows full-duplex synchronous communication. Both the
receiver and transmitter can select either an internal or external clock. The HDLC
module encapsulates data within opening and closing flags, and sixteen bits of CRC
precedes the closing flag. All information between the opening and closing flag is
zero-stuffed; that is, if five consecutive ones occur, independent of byte
boundaries, a zero is automatically inserted by the transmitter and automatically
deleted by the receiver. This allows a flag byte (07Eh) to be unique within a serial
stream. The standard CRC-CCITT polynomial
(x16 + x12 + x5 + 1)
is implemented, with
the generator and checker preset to all ones.
HDLC module
structure
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
R e c e i v e a n d t r a n s m i t o p e r a t i o n s
Both receive and transmit operations are essentially automatic.
Receive
FIFO
Interface
Transmit
FIFO
Interface
Wrapper
be
[1
:0
]
d
a
ta
[31:
0]
read
wr
it
e
be
[1
:0
]
d
a
ta
[31:
0]
st
at
us
[6
:0]
AHB Bus
ref_clk
va
lid
int
HDLC
RCLK
TXD
RXD
IO Hub
TCLK
Summary of Contents for NS9215
Page 1: ...NS9215 Hardware Reference 90000847_C Release date 10 April 2008...
Page 3: ......
Page 4: ......
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...