DS21Q42 Просмотр технического описания (PDF) - Maxim Integrated
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DS21Q42 Datasheet PDF : 116 Pages
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DS21Q42
FUNCTIONAL DESCRIPTION
The receive side framer locates D4 (SLC–96) or ESF multiframe boundaries as well as detects incoming
alarms including, carrier loss, loss of synchronization, blue (AIS) and yellow alarms. If needed, the
receive side elastic store can be enabled in order to absorb the phase and frequency differences between
the recovered T1 data stream and an asynchronous backplane clock which is provided at the RSYSCLK
input. The clock applied at the RSYSCLK input can be either a 2.048 MHz clock or a 1.544 MHz clock.
The RSYSCLK can be a burst clock with speeds up to 8.192 MHz.
The transmit side of the DS21Q42 is totally independent from the receive side in both the clock
requirements and characteristics. Data off of a backplane can be passed through a transmit side elastic
store if necessary. The transmit formatter will provide the necessary frame/multiframe data overhead for
T1 transmission.
READER’S NOTE:
This data sheet assumes a particular nomenclature of the T1 operating environment. In each 125 us
frame, there are 24 8–bit channels plus a framing bit. It is assumed that the framing bit is sent first
followed by channel 1. Each channel is made up of 8 bits which are numbered 1 to 8. Bit number 1 is
the MSB and is transmitted first. Bit number 8 is the LSB and is transmitted last. Throughout this data
sheet, the following abbreviations will be used:
D4
SLC–96
ESF
B8ZS
CRC
Ft
Fs
FPS
MF
BOC
HDLC
FDL
Superframe (12 frames per multiframe) Multiframe Structure
Subscriber Loop Carrier – 96 Channels (SLC–96 is an AT&T registered trademark)
Extended Superframe (24 frames per multiframe) Multiframe Structure
Bipolar with 8 Zero Substitution
Cyclical Redundancy Check
Terminal Framing Pattern in D4
Signaling Framing Pattern in D4
Framing Pattern in ESF
Multiframe
Bit Oriented Code
High Level Data Link Control
Facility Data Link
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