DS21354/DS21554 3.3V/5V E1 Single-Chip Transceivers
1.1. Functional Description
The analog AMI/HDB3 waveform off the E1 line is transformer coupled into the RRING and RTIP pins
of the DS21354/554. 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 DS21354/DS21554 contain an active filter that reconstructs the analog-
received signal for the nonlinear losses that occur in transmission. The devices have a usable receive
sensitivity of 0 to -43dB, which allows the device to operate on cables over 2km in length. The receive-
side framer locates 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 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 2.048MHz/4.096MHz/8.192MHz clock or a 1.544MHz
clock.
The transmit-side framer is totally independent from the receive side in both the clock requirements and
characteristics. Data off a backplane can be passed through a transmit-side elastic store if necessary. The
transmit formatter provides the necessary frame/multiframe data overhead for E1 transmission.
Reader’s Note: This data sheet assumes a particular nomenclature of the E1 operating environment. In
each 125ꢀs frame, there are 32 eight-bit time slots numbered 0 to 31. Time slot 0 is transmitted first and
received first. These 32 time slots are also referred to as channels with a numbering scheme of 1 to 32.
Time slot 0 is identical to channel 1, time slot 1 is identical to Channel 2, and so on. Each time slot (or
channel) is made up of eight bits, which are numbered 1 to 8. Bit number 1 is the most significant bit
(MSB) and is transmitted first. Bit number 8 is the least significant bit (LSB) and is transmitted last. The
term “locked” refers to two clock signals that are phase or frequency locked, or derived from a common
clock (i.e., a 1.544MHz clock may be locked to a 2.048MHz clock if they share the same 8kHz
component). Throughout this data sheet, the following abbreviations are used:
NAME
FAS
CAS
MF
FUNCTION
Frame-Alignment Signal
Channel-Associated Signaling
Multiframe
Si
International Bits
CRC4
CCS
Sa
Cyclical Redundancy Check
Common-Channel Signaling
Additional Bits
E-Bit
CRC4 Error Bits
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