
DS26519 16-Port T1/E1/J1 Transceiver 
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9.9.6.1 Additional E1 Receive Sa- and Si-Bit Receive Operation (E1 Mode) 
The DS26519, when operated in the E1 mode, provides for access to both the Sa and the Si bits via two methods. 
The first involves using the internal 
E1RAF
/
E1RNAF
 and 
E1TAF
/
E1TNAF
 registers. The second method involves 
an expanded version of the first method. 
9.9.6.1.1 Internal Register Scheme Based on Double-Frame (Method 1) 
On the receive side, the 
E1RAF
 and 
E1RNAF
 registers will always report the data as it received in the Sa and Si bit 
locations. The 
E1RAF
and 
E1RNAF
 registers are updated on align frame boundaries. The setting of the Receive 
Align Frame bit in Receive Latched Status Register 2 (
RLS2
.0) will indicate that the contents of the RAF and RNAF 
have been updated. The host can use the 
RLS2
.0 bit to know when to read the 
E1RAF
 and 
E1RNAF
 registers. The 
host has 250
μ
s to retrieve the data before it is lost. 
9.9.6.1.2 Internal Register Scheme Based on CRC-4 Multiframe (Receive) 
On the receive side, there is a set of eight registers (
E1RsiAF
, 
E1RSiNAF
, 
E1RRA
, 
E1RSa4
 to E1RSa8) that report 
the Si and Sa bits as they are received. These registers are updated with the setting of the receive CRC-4 
multiframe bit in Receive Latched Status Register 2 (
RLS2
.1). The host can use the 
RLS2
.1 bit to know when to 
read these registers. The user has 2ms to retrieve the data before it is lost. See the register descriptions for 
additional information. 
9.9.6.1.3 Internal Register Scheme Based on CRC-4 Multiframe (Transmit) 
On the transmit side there is a set of eight registers (
E1TSiAF
, 
E1TSiNAF
, 
E1TRA
, 
E1TSa4
 to 
E1TSa8
) that, via 
the E1 Transmit Sa-Bit Control Register (
E1TSACR
), can be programmed to insert both Si and Sa data. Data is 
sampled from these registers with the setting of the transmit multiframe bit in Transmit Latched Status Register 1 
(
TLS1
.3). The host can use the TLS1.3 bit to know when to update these registers. It has 2ms to update the data or 
else the old data will be retransmitted. See the register descriptions in Section 
10
 for more information. 
9.9.6.2 Sa-Bit Monitoring and Reporting 
In addition to the registers outlined above, the DS26519 provides status and interrupt capability in order to detect 
changes in the state of selected Sa bits. The 
E1RSAIMR
register can be used to select which Sa bits are 
monitored for a change of state. When a change of state is detected in one of the enabled Sa bit positions, a status 
bit is set in the 
RLS7
 register via the SaXCD bit (bit 0). This status bit can in turn be used to generate an interrupt 
by unmasking 
RIM7
.0 (SaXCD). If multiple Sa bits have been enabled, the user can read the 
SaBITS
 register at 
address 06Eh to determine the current value of each Sa bit.  
For the Sa6 bits, additional support is available to detect specific codewords per ETS 300 233. The Sa6CODE 
register will report the received Sa6 codeword. The codeword must be stable for a period of three submultiframes 
and be different from the previous stored value in order to be updated in this register. See the 
Sa6CODE
 register 
description for further details on the operation of this register and the values reported in it. An additional status bit is 
provided in 
RLS7
.1 (Sa6CD) to indicate if the received Sa6 codeword has changed. A mask bit is provided for this 
status bit in 
RIM7
 to allow for interrupt generation when enabled. 
9.9.7 Maintenance and Alarms 
The DS26519 provides extensive functions for alarm detection and generation. It also provides diagnostic functions 
for monitoring of performance and sending of diagnostic information: 
 
Real-time and latched status bits, interrupts and interrupt mask for transmitter and receiver 
 
LOS detection 
 
RIA detection and generation 
 
Error counters 
 
DS0 monitoring  
 
Milliwatt generation and detection 
 
Slip buffer status for transmit and receive