Datasheet

DS21Q50
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Note: This data sheet assumes a particular nomenclature of the E1 operating environment. In each 125µs
frame, there are 32 8-bit time slots numbered 0 to 31. Time slot 0 is transmitted first and received first.
These 32 time slots are also referred to as channels with a numbering scheme of 1 to 32. Time slot 0 is
identical to channel 1; time slot 1 is identical to channel 2; and so on. Each time slot (or channel) is made
up of eight bits that are numbered 1 to 8. Bit number 1, MSB, is transmitted first. Bit number 8, the LSB,
is transmitted last. The term “locked” is used to refer to two clock signals that are phase-locked or
frequency-locked or derived from a common clock (i.e., a 8.192MHz clock can be locked to a 2.048MHz
clock if they share the same 8kHz component). Throughout this data sheet, the following abbreviations
are used:
NAME FUNCTION
FAS Frame Alignment Signal
CAS Channel Associated Signaling
MF Multiframe
Si International bits
CRC4 Cyclical Redundancy Check
CCS Common Channel Signaling
Sa Additional bits
E-Bit CRC4 Error Bits
LOC Loss of Clock
TCLK
This generally refers to the transmit rate clock and can reference an actual input
signal to the device (TCLK) or an internally derived signal used for transmission.
RCLK
This generally refers to the recovered network clock and can be a reference to an
actual output signal from the device or an internal signal.