txc-03456 TranSwitch Corporation, txc-03456 Datasheet - Page 41

• Manufacturer Part Number: txc-03456
• Description: Device Level Mapper
• Manufacturer: TranSwitch Corporation

Pointer Tracking Feature
The pointer tracking feature is enabled by placing a high on the PTEN lead (pin 2). The AU-4 pointer is carried
in the H1 and H2 bytes. The starting location for the frame is determined by the C1 pulse present in the DC1J1
or DC1 signal lead. When the pointer tracking feature is enabled, the J1 pulse in the DC1J1 signal must not be
present, nor is the DSPE signal required. The pointer tracking machine derives the starting location of the J1
byte and the other VC-4 bytes. The pointer tracking state machine is compliant with the ETSI state machine
specified in the ETSI 1015 document. A logic diagram of the state machine is shown in Figure 22. No addi-
tional states or transitions have been added to the pointer state machine.
For North American applications, a control bit is provided for disabling the AIS to LOP transition, which is
shown as a dotted line in Figure 22. This transition is disabled by writing a 1 to control bit PADS (bit 1 in 18H).
In addition, control bits are provided which permit the value of the S-bits (H1 byte) in the pointer tracking
machine to be disabled, equal to 10, or to a microprocessor-written value.
incr. offset
inc_ind
offset undefined
8*inv_point
LOP
INC
accept new offset
offset undefined
3*new_point
8*NDF_enable
Note: The AIS to LOP transition is not specified for North American applications,
and can be disabled by setting the PADS control bit to a 1.
Figure 22. Pointer Interpretation State Diagram
accept new offset
3*any_point
accept new offset
3*new_point
NORM
offset undefined
accept new offset
DATA SHEET
3*AIS_ind
- 41 -
3*new_point
from all states
decr. offset
dec_ind
DEC
NDF
AIS
accept new offset
NDF_enable
Ed. 1A, January 2000
TXC-03456
TXC-03456-MB
L4M