
Advance Information
MT9072
55
5.1
Transmit Elastic Buffer
In T1 mode, the MT9072 contains a transmit elastic buffer in addition to the receive elastic buffer. Data is
clocked into the transmit elastic buffer by the 2.048 Mbit/s or 8.192 Mbit/s ST-BUS clock input to the CKi pin.
The data is clocked out of the transmit elastic buffer by the 1.544MHz clock input to the TXCL pin.
The delay through the transmit elastic buffer will vary in accordance with the position of the channel in the
frame. For example, PCM24 channel 1 sits in the elastic buffer for approximately 1 usec, and PCM24 channel
24 sits in the elastic buffer for approximately 32 usec. The relative phase delay between the system ST-BUS
frame boundary and the transmit elastic frame read boundary is measured every frame and reported in the
Transmit Slip Buffer Status Word (Y14). In addition, the relative delay between these frame boundaries may be
programmed by writing to Tx Set Delay Bits (register address YF7). Every write to the TX Set Delay Bits resets
Register
Address
Register
Description
Y00
Framing Mode Select
If IMA mode is selected the transmit and receive elastic buffers
are bypassed.
Y13
Receive Slip Buffer Status Word
This register provides status bits for receive slip and its direction
word that indicates the phase difference between the ST-BUS
and the PCM24
Y14
Transmit Slip Buffer Status Word
This register provides status bit for transmit slip and its direction
word that indicates the phase difference between the ST-BUS
and the PCM24.
Y26
Elastic Store and Excessive Zero
Status Latch
This register indicates the latched version of the slip indicator
bits from registers Y13 and Y14.
Y36
Elastic Store and Excessive Zero
Interrupt Status
Interrupt status word for the slip indicators.
Y46
Elastic Store and Excessive Zero
Interrupt Mask
Interrupt mask bits for the slip indicators.
YF7
Transmit Set Delay Bits
This register sets a one time delay through the transmit slip
buffer.
Table 14 - Registers Related to the Elastic Buffer (T1)
Register
Address
Register
Description
Y00
Y03
Framing Mode Select.
DL,CCS,CAS and Other
Control Register
Sync and CRC-4 Remote
status
Phase Status Indicator
If IMA mode is selected the receive elastic buffers are bypassed.
ELAS bit is used to bypass the elastic store, that data at DSTo is
the received. PCM30 data after the HDB3 coding.
RSLP and RSLPD show the slip and the direction of the slip.
Y10
Y14
This word reflects the delay through the receive elastic store
from the line to the ST-BUS side.
RSLIPI in this register reflects the interrupt due to a slip.
Y34
Sync,CRC-4 Remote, Alarm,
MAS and Phase Status Word
Sync,CRC-4 Remote, Alarm,
MAS and Phase Status Word
Interrupt Mask
Table 15 - Registers Related to Elastic Store (E1)
Y44
Interrupt mask bits for the slip indicator.