
DS26518 8-Port T1/E1/J1 Transceiver 
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9.4 
Initialization and Configuration 
9.4.1 Example Device Initialization and Sequence 
STEP 1: Reset the device by pulling the 
RESETB
 pin low, applying power to the device, or by using the software 
reset bits outlined in Section 
9.2.2
. Clear all reset bits. Allow time for the reset recovery. 
STEP 2: Check the Device ID in the 
IDR
 register. 
STEP 3: Write the 
GTCCR1 
register to correctly configure the system clocks. If supplying a 1.544MHz MCLK 
follows this write with at least a 300ns delay in order to allow the clock system to properly adjust. 
STEP 4: Write the entire remainder of the register space for each port with 00h, including reserved register 
locations. 
STEP 5: Choose T1/J1 or E1 operation for the framers by configuring the T1/E1 bit in the 
TMMR
 and 
RMMR
registers for each framer. Set the FRM_EN bit to 1 in the 
TMMR
 and 
RMMR
 registers. If using software transmit 
signaling in E1 mode, program the 
E1TAF
 and 
E1TNAF
 registers as required. Configure the framer Transmit 
Control Registers (
TCR1
–
TCR4
). Configure the framer Receive Control Registers (
RCR1
–
RCR3
). Configure other 
framer features as appropriate. 
STEP 6: Choose T1/J1 or E1 operation for the LIUs by configuring the T1J1E1S bit in the 
LTRCR
 register. 
Configure the line build-out for each LIU. Configure other LIU features as appropriate. Set the TE (transmit enable) 
bit to turn on the TTIPn and TRINGn outputs. 
STEP 7: Configure the elastic stores, HDLC controller, and BERT as needed. 
STEP 8: Set the INIT_DONE bit in the 
TMMR
 and 
RMMR
 registers for each framer. 
9.5 
Global Resources 
All eight framers share a common microprocessor port and a common MCLK. There is a common software 
configurable BPCLK1 output. A set of global registers includes global resets, global interrupt status, interrupt 
masking, clock configuration, and the device ID register. See the global register bit map in 
Table 10-6
. A common 
JTAG controller is used for all ports. 
9.6 
Per-Port Resources 
Each port has an associated framer, LIU, BERT, jitter attenuator, and transmit/receive HDLC controller. Each of the 
per-port functions has its own register space. 
9.7 
Device Interrupts 
Figure 9-10
 diagrams the flow of interrupt conditions from their source status bits through the multiple levels of 
information registers and mask bits to the interrupt pin. When an interrupt occurs, the host can read the global 
interrupt information registers 
GFISR1
, 
GLISR1
, and 
GBISR1
 to quickly identify which of the eight transceivers is 
(are) causing the interrupt(s). The host can then read the specific transceiver’s interrupt information registers (
TIIR
, 
RIIR
) and the latched status registers (
LLSR
, 
BLSR
) to further identify the source of the interrupt(s). If TIIR or RIIR 
is the source, the host reads the transmit latched status or the receive latched status registers for the source of the 
interrupt. All interrupt information register bits are real-time bits that clear once the appropriate interrupt has been 
serviced and cleared, as long as no additional, unmasked interrupt condition is present in the associated status 
register. All latched status bits must be cleared by the host writing a “1” to the bit location of the interrupt condition 
that has been serviced. Latched status bits that have been masked via the interrupt mask registers are masked 
from the interrupt information registers. The interrupt mask register bits prevent individual latched status conditions 
from generating an interrupt, but they do not prevent the latched status bits from being set. Therefore, when 
servicing interrupts, the user should XOR the latched status with the associated interrupt mask in order to exclude 
bits for which the user wished to prevent interrupt service. This architecture allows the application host to 
periodically poll the latched status bits for noninterrupt conditions, while using only one set of registers.