Datasheet

DS2155
83 of 238
16. SIGNALING OPERATION
There are two methods to access receive signaling data and provide transmit signaling data, processor-
based (software-based) or hardware-based. Processor-based refers to access through the transmit and
receive signaling registers RS1–RS16 and TS1–TS16. Hardware-based refers to the TSIG and RSIG pins.
Both methods can be used simultaneously.
16.1 Receive Signaling
Figure 16-1. Simplified Diagram of Receive Signaling Path
16.1.1 Processor-Based Signaling
The robbed-bit signaling (T1) or TS16 CAS signaling (E1) is sampled in the receive data stream and
copied into the receive signaling registers, RS1–RS16. In T1 mode, only RS1–RS12 are used. The
signaling information in these registers is always updated on multiframe boundaries. This function is
always enabled.
16.1.1.1 Change-of-State
To avoid constant monitoring of the receive signaling registers, the DS2155 can be programmed to alert
the host when any specific channel or channels undergo a change of their signaling state.
RSCSE1–RSCSE4 for E1 and RSCSE1–RSCSE3 for T1 are used to select which channels can cause a
change-of-state indication. The change-of-state is indicated in status register 5 (SR1.5). If signaling
integration (CCR1.5) is enabled, then the new signaling state must be constant for three multiframes
before a change-of-state is indicated. The user can enable the INT pin to toggle low upon detection of a
change in signaling by setting the IMR1.5 bit. The signaling integration mode is global and cannot be
enabled on a channel-by-channel basis.
The user can identity which channels have undergone a signaling change-of-state by reading the
RSINFO1–RSINFO4 registers. The information from these registers inform the user which RSx register
to read for the new signaling data. All changes are indicated in the RSINFO1–RSINFO4 registers
regardless of the RSCSE1–RSCSE4 registers.
RECEIVE SIGNALING
REGISTERS
CHANGE-OF-STATE
INDICATION
REGISTERS
SIGNALING
BUFFERS
A
LL-ONES
REINSERTION
CONTROL
RSER
RSYNC
RSIG
T1/E1 DATA STREAM
PER-CHANNEL
CONTROL
SIGNALING
EXTRACTION