
Advance Information
MT9072
59
6.2.1.3 E1 Data Link (DL) Pin Data Received on PCM30 - With Elastic Buffer
In this case, the TxDLC pin is used for both DL data transmitted on the PCM30 link and DL data received on
the PCM30 link. However, instead of using the non-buffered data output at the RxDL pin, the buffered DSTo
output data is used. The clock at the TxDLC pin clocks data from the DSTo ST-BUS stream into an external
controller, or the enable signal at the TxDLC pin enables a 2.048Mbit/s clock which clocks data from the DSTo
ST-BUS stream into an external controller. Since a common clock is used for both transmit and receive, a
simpler data controller may be used such as the MT8952B. However, DL data will be lost or repeated when a
receive frame slip occurs, as the DL data does pass through the elastic buffer. See Figures 59 - 60 for timing
requirements.
6.2.2
When the National Bit Buffer transmit data registers access is enabled, the settings of 40 data bits in 5
registers (address YB0-YB4) determine the Data Link (DL) output on the PCM30 link corresponding to bit
positions Sa4-8 over one complete CRC-4 Multiframe. The CRC-4 alignment status bit CALN (register address
Y11) and corresponding maskable interrupt status bit CALNI (register address Y36) indicate the beginning of
every received CRC-4 multiframe. Data for DL transmission should be written to the National Bit Buffer transmit
data registers immediately following the CALN status indication (during basic frame 0) and before the start of
basic frame 1.
E1 Data Link (DL) National Bit Buffer Access
Table 18 illustrates the organization of the MT9072 transmit and receive national bit buffers. Each row is an
addressable byte of the MT9072 national bit buffer, and each column contains the national bits of an odd
numbered frame of each CRC-4 Multiframe. The transmit and receive national bit buffers are located at
addresses YB0 to YB4 and YC0 to YC4 respectively.
For the National Bit Buffer transmit registers DL access to be enabled the SA4SS to SA8SS(register Y08) are
set to 00.
Similarly, the DL data received on the PCM30 link is output to the National Bit Buffer receive data registers
(register address YC0-YC4), corresponding to bit positions as shown in Table 18. However, the National Bit
Buffer receive data registers are always enabled, regardless of the above control bit settings(SA4SS to
SA8SS). Received DL Data should be read from the National Bit Buffer receive data registers immediately
following the CALN status indication (during basic frame 0) and before the start of basic frame 1.
In order to facilitate conformance to ETS 300 233, three maskable interrupts are available for change of state of
Sa bits in the receive National Bit Buffer. These include Eight Consecutive Sa6 Nibbles (Sa6N8), Sa6 Nibble
Change (Sa6N) and Sa Nibble Change (SaN). See the detailed descriptions for these status bits provided in
the CAS, National, CRC-4 Local and Timer Interrupt Status Register (address Y36).
6.2.3
When the ST-BUS Data Link (DL) access is enabled, the setting of the 8 ST-BUS DSTi data bits determine the
Data Link (DL) output on the PCM30 link corresponding to bit positions one to three and Sa4-8 over each Non-
E1 Data Link (DL) ST-BUS Access
Addressable Bytes
NFAS Frames of a CRC-4 Multiframe
Transmit
Address
Receive
Address
F1
B7
F3
B6
F5
B5
F7
B4
F9
B3
F11
B2
F13
B1
F15
B0
TN0
YB0
RN0
YC0
S
a4
S
a4
S
a4
S
a4
S
a4
S
a4
S
a4
S
a4
TN1
YB1
RN1
YC1
S
a5
S
a5
S
a5
S
a5
S
a5
S
a5
S
a5
S
a5
TN2
YB2
RN2
YC2
S
a6
S
a6
S
a6
S
a6
S
a6
S
a6
S
a6
S
a6
TN3
YB3
RN3
YC3
S
a7
S
a7
S
a7
S
a7
S
a7
S
a7
S
a7
S
a7
TN4
YB4
RN4
YC4
S
a8
S
a8
S
a8
S
a8
S
a8
S
a8
S
a8
S
a8
Table 18 - MT9072 National Bit Buffers (E1)