TMXF28155 Supermapper
155/51 Mbits/s SONET/SDH x28/x21 DS1/E1
Data Sheet
June 2002
546
Agere Systems Inc.
21 28-Channel Framer Block Functional Description
(continued)
5-9102(F)r.1
Figure 81. Network Serial Multiplexed Interface (Multiple Octets)
21.27.4 Time-Slot Sequencing
I
Link numbers—28 link numbers, numbered 1 to 28 in T1 mode, and 1 to 21 for E1 mode.
Note:
Link numbers can start at 0 by setting FRM_LNKSTART (
Table 359 on page 261
) bit 8 at address 0x80050
to 0. This will cause the link numbers for T1 to be numbered 0—27 and for E1, 0—20.
I
In T1 mode, each of the 28 links has 24 time slots and should be numbered 1 to 24.
I
In E1 mode, each of the 21 links has 32 time slots and should be numbered 0 to 31.
I
The FSYNC (
Table 619 on page 545
) bit indicates that the data for the link is in the first time slot for that frame
(time slot 1 in T1 and time slot 0 in E1 mode).
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Link data is sent out in any order. It is totally unpredictable. Time slots are sent in order and it is the job of the
switch
to keep track of which time slot it receives.
Note:
The order of the links sent out is in relation to the order in which the Supermapper framer receives the links.
Thus it is possible, for example, to receive all the time slots for link 5 and then start the next frame of data for
link 5 before link 10 completes its frame.
The minimum and maximum time between successive time slots on a link is calculated below for both DS1
and E1, using an NSMI bus clock of 51.84 MHz (19.3 ns clock period).
DS1:
Max time = (1 link time-slot interval) + (27 links * 8 bits * NSMI clk period) + (1 link bit time).
Max time = 5.2 μs + (27 * 8 * 19.3 ns) + (648 ns) = 10 μs.
Min time = (1 link time-slot interval) – (27 links * 8 bits * NSMI clk period).
Min time = 5.2 μs – (27 * 8 * 19.3 ns) = 1.0 μs.
E1:
Max time = (1 link time-slot interval) + (20 links * 8 bits * NSMI clk period).
Max time = 3.9 μs + (20 * 8 * 19.3 ns) = 7.0 μs.
Min time = (1 link time-slot interval) – (20 links * 8 bits * NSMI clk period).
Min time = 3.9 μs – (20 * 8 * 19.3 ns) = 0.8 μs.
21.27.5 Timing Between Transmit and Receive
6-Pin Mode.
The Supermapper sends out the data and link information through the transmit signals. While it sends
data, it also expects data to be sent back for the same link number and time slot. The only requirement the Super-
mapper has is that it receives data at a constant time interval every time. For example, at clock 1, data and link
information was sent to the
switch
. Then at clock 16, data was sent back to the Supermapper. Thus, the time
taken to send data back was 15 clocks. During this time, the next link and data were sent to the
switch
at clock 9,
and the Supermapper must receive the second data requested at clock 24. The time interval
must
be constant. It
doesn’t matter how long, but it
must
be constant.
START
SERIAL DATA
MSB
LSB
SERIAL DATA
SERIAL DATA
START
START
LINETXCLK29
LINETXDATA29
LINETXSYNC29