PMC-Sierra, Inc.
PM4541T1XC-EVBD
TELECOM STANDARD PRODUCT
PMC-920314
ISSUE 2
T1XC EVALUATION DAUGHTERBOARD
2.3 Decode Logic
Decode logic is provided on the daughterboard to give memory mapped access to
all of the registers within both T1XCs. Registers within the "east" T1XC are
accessible starting at address C000H. Registers within the "west" T1XC are
accessible starting at address C100H. Additional chip selects are provided for
addresses C200H-C2FFH and C300H-C3FFH for use on the prototype area.
2.4 DIP Switches
The DIP Switch Block controls the operational modes of the MT8940 DPLL device
that is used to generate the backplane clock. The various modes of the device are
selected by DIP switch settings. Access to the enable inputs for the various clock
outputs is also provided through these switches.
2.5 Clock DPLL
The MT8940 T1/CEPT Digital Trunk DPLL can provide a number of different clocks
with different methods of synchronization, depending upon its mode setting, which
can be used to drive the backplane interface of the T1XCs. The device can output
1.544 MHz, 2.048 MHz, and 4.096 MHz clocks in true or complement format. The
DPLL can be allowed to free-run or it can be synchronized to the receive frame
pulses of either T1XC. PLL control is accomplished with the DIP switches
connected to the inputs.
2.6 Oscillators
Up to four oscillators can be used on the T1XC EVBD daughterboard depending
upon the choice of configuration. The T1XC devices require a 37.056 MHz clock if
all of the device's features are to be utilized. Although two oscillator sockets are
provided, only a single oscillator is necessary if two T1XC devices are used. The
insertion of a jumper (J25) will join the two T1XC XCLK inputs together to allow the
single clock to drive both devices. If an E1XC device is used in place of one of the
T1XC devices then the jumper must be removed to isolate each clock line and a
49.152 MHz oscillator is used to drive the E1XC XCLK input.
The MT8940 DPLL device requires two oscillators to drive internal DPLLs, one at
12.355 MHz, and the other at 16.384 MHz. If the MT8940 is removed from the
daughterboard, then these oscillators can be replaced with ones directly compatible
with the backplane rate. Each oscillator output is directly accessible at header pins,
allowing connections to be made by connecting jumpers to the T1XC devices.
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PMC [ PMC-SIERRA, INC ]
