DS2154
FUNCTIONAL DESCRIPTION
The analog AMI/HDB3 waveform off of the E1 line is transformer coupled into the RRING and RTIP
pins of the DS2154. The device recovers clock and data from the analog signal and passes it through the
jitter attenuation mux to the receive side framer where the digital serial stream is analyzed to locate the
framing/multiframe pattern. The DS2154 contains an active filter that reconstructs the analog received
signal for the non-linear losses that occur in transmission. The device has a usable receive sensitivity of 0
dB to -43 dB which allows the device to operate on cables over 2 km in length. The receive side framer
locates the FAS frame and CRC and CAS multiframe boundaries as well as detects incoming alarms
including, carrier loss, loss of synchronization, AIS, and Remote Alarm. If needed, the receive side elastic
store can be enabled in order to absorb the phase and frequency differences between the recovered E1
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 also be a bursty clock with speeds up to 8.192 MHz.
The transmit side of the DS2154 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
E1 transmission. Once the data stream has been prepared for transmission, it is sent via the jitter
attenuation mux to the waveshaping and line driver functions. The DS2154 will drive the E1 line from the
TTIP and TRING pins via a coupling transformer. The line driver can handle both 75Ω=and 120Ω=lines
and it has options for high return loss applications. The line driver contains a current limiter that will
restrict the maximum current into a 1Ω=load to less than 50 mA (rms).
READER’S NOTE
This data sheet assumes a particular nomenclature of the E1 operating environment. There are 32 8-bit
timeslots in an E1 systems which are number 0 to 31. Timeslot 0 is transmitted first and received first.
These 32 timeslots are also referred to as channels with a numbering scheme of 1 to 32. Timeslot 0 is
identical to channel 1, timeslot 1 is identical to Channel 2, and so on. Each timeslot (or 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:
FAS
CAS
MF
Si
Frame Alignment Signal
Channel Associated Signaling
Multiframe
CRC4
CCS
Sa
Cyclical Redundancy Check
Common Channel Signaling
Additional bits
International bits
E-bit
CRC4 Error bits
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DALLAS [ DALLAS SEMICONDUCTOR ]
