71
The received 4 data bits previous to reception of the violation
pulse have not been the sequence BX00 (where X = don't
care). The error signal (ERR) remains low.
NOTES:
1. The data sequences B000V and BB00V are valid HDB3 codings
of the NRZ binary sequence 10000.
2. Theerrorsignal(ERR)count,istheaccuratenumberofallsingle
bit errors.
AMl Signals HDB3/AMl = Low
- A coding error (ERR) is signaled when a violation pulse
(+V) is received.
In Either the HDB3 or AMI Mode
- When high levels appear simultaneously on both HDB3
inputs (+ HDB3 IN, -HDB3 IN) a logical one is assumed
in the HDB3/AMl input stream and the error signal
(ERR) goes high for the duration of the violation.
Alarm Inhibit Signal
- The alarm output (AIS) is set high if, in two successive
periods of the external Reset Alarm Signal (RAlS), less
than three zeros are received.
- The alarm output (AlS) is reset low when three or more
zeros are received during two Reset Alarm Signal periods.
Transcoder Operation
Transmitter Coder (See Figure 1)
The HDB3/AMI transmitter coder operates on 4-bit serial
strings of NRZ binary data and a synchronous transmitter
clock (CTX). NRZ binary data is serially clocked into the
transmitter on the negative transition of the (CTX) clock.
HDB3/AMI coding is performed on the 4-bit string, and
HDB3/AMI binary output data is clocked out to the (+HDB3
OUT, -HDB3 OUT) outputs on the positive transition of the
transmitter clock (CTX) 3 1/2 clock pulses after the data
appeared at the (NRZ-IN) input.
Receiver Decoder (See Figure 2)
The HDB3/AMI receiver decoder operates on 4-bit serial
strings of binary coded HDB3/AMI signals, and a synchro-
nous receiver clock (CRX), HDB3/AMI binary data is serially
clocked into the receiver on the positive transition of the
(CRX) clock. HDB3/AMI decoding is performed on the 4-bit
string, and NRZ binary output data is clocked out to the
(NRZ-OUT) output on the positive transition of the receiver
clock (CRX) 4 clock pulses after the data appeared at the
(+HDB3 IN, -HDB3 IN) inputs.
HANDLING DELAY
NRZ - IN
+HDB3 OUT
HDB3
CODED
-HDB3 OUT
EXTERNAL GENERATED
TERNERY HDB3
+HDB3 OUT
AMI
CODED
-HDB3 OUT
EXTERNAL GENERATED
AMI
CTX
FIGURE 1. TRANSMITTER CODER OPERATION TIMING WAVEFORMS - NRZ TO HDB3/AMI CODING
CD22103A