Data Sheet
June 2002
TMXF28155 Supermapper
155/51 Mbits/s SONET/SDH x28/x21 DS1/E1
579
Agere Systems Inc.
23 Digital Jitter Attenuation Controller Functional Description
(continued)
23.3 Functional Block Diagram of the DJA Block
The functional view of the DJA block, along with interconnections to the other blocks within the Supermapper
device, is shown in
Figure 100
.
The DJA block interfaces only to the cross connect and microprocessor interface blocks within the Supermapper
device. The input interface between the DJA block and the cross connect block consists of clock, serial data, VT
pointer adjustment indication, and AIS insert indication. The output interface consists of clock, serial data, and AIS
insert indication, as well as the DS1 and E1 AIS clocks for use by other blocks within the device.
5-8956(F)r.1
Figure 100. Basic Functional Flow of the DJA Block
23.4 Digital Jitter Attenuation Controller Operation
The digital jitter attenuation (DJA) controller is comprised of 28 DJA blocks. The DJA_SEL line rate control register
(
Table 490
) is used to determine if the block is operating in the DS1 or E1 mode (1 = DS1, 0 = E1).
The DJA controller requires a reference clock running at 16 or 32 times the line rate of the signal requiring jitter
attenuation. This reference clock should be driven on one of the external input signals DS1XCLK or E1XCLK (see
Table 3, High-Speed I/O Pin Descriptions, on page 17
, under the M13 MUX/DEMUX block receive path section).
Each jitter attenuator block receives a clock, data, pointer adjust control, and an AIS control signal input. If the AIS
control signal is active (high) on any time slot, and the AIS control (DJA_DS1SCALE bit 1; see
Table 487 on
page 338
) is enabled, then the AIS clock generation block (see
Figure 100
) of the DJA simply divides the correct
XCLK by 16 or 32 (either DS1_XCLK or E1_XCLK), via the DJA_BLUECLKD register shown in
Table 491
, inde-
pendent of being in DS1 or E1 mode, sends this divided clock (DS1_AISCLK or E1_AISCLK) to the cross connect,
and transmits the data signal (DJA_DATA) as a continuous logic 1.
Note:
Enabling the automatic AIS clock selection will result in FRAMER lockup under extreme conditions (refer to
Errata issue 510).
Even with the digital PLL portion of the DJA turned off (via the P_DJA_CLK_EN register; see
Table 81 on
page 73
), the AIS clock generation block will still generate the correct DS1_AISCLK or E1_AISCLK signals.
Each DJA block has a 64-bit elastic store. These elastic stores are monitored for both underflow and overflow con-
ditions. Both of these conditions contribute to the DJA_ESOVFL parameter, which can be unmasked to contribute
to an interrupt DJA_ESOVFL[28:1] (
Table 481 on page 337
). In the event of an elastic store overflow, the elastic
store will re-center itself.
The block monitors DS1XCLK (DJA_DS1LOC and DJA_G_DS1LOC) and E1XCLK (DJA_E1LOC and
DJA_G_E1LOC) for loss of clock (LOC indication,
Table 483 on page 338
) and change of loss of clock state (LOC
delta,
Table 481
). The DJA_DS1LOC and DJA_E1LOC parameters are controlled by LOC events detected at the
AIS clock generation block, while the DJA_G_DS1LOC and DJA_G_E1LOC parameters are controlled by LOC
events detected at the DPLL. All loss of clock indications can contribute to a DJA interrupt. These interrupts can be
unmasked by writing zeros to the registers in
Table 482 on page 337
.
XC_JAISx
XC_JCLKx
XC_JDATAx
XC_JPTRADJx
DS1_XCLK
JITTER
E1_XCLK
DJA_CLKx
DJA_DATAx
BLOCK REPEATED 28 TIMES
AIS CLOCK
GENERATION
DS1_AISCLK
E1_AISCLK
ATTENUATION
BLOCK
DJA_AUTOAISx