DS21FT44/DS21FF44
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7. DS21Q44 PIN FUNCTION DESCRIPTION
This section describes the signals on the DS21Q44 die. Signals which are not bonded out or have limited
functionality in the DS21FT44 and DS21FF44 are noted in italics.
TRANSMIT SIDE PINS
Signal Name:
TCLK
Signal Description:
Transmit Clock
Signal Type:
Input
A 2.048 MHz primary clock. Used to clock data through the transmit side formatter.
Signal Name:
TSER
Signal Description:
Transmit Serial Data
Signal Type:
Input
Transmit NRZ serial data. Sampled on the falling edge of TCLK when the transmit side elastic store is
disabled. Sampled on the falling edge of TSYSCLK when the transmit side elastic store is enabled.
Signal Name:
TCHCLK
Signal Description:
Transmit Channel Clock
Signal Type:
Output
A 256 KHz clock which pulses high during the LSB of each channel. Synchronous with TCLK when the
transmit side elastic store is disabled. Synchronous with TSYSCLK when the transmit side elastic store
is enabled. Useful for parallel to serial conversion of channel data. This function is available when FMS
= 1 (DS21Q43 emulation). This signal is not bonded out in the DS21FF44/DS21FT44.
Signal Name:
TCHBLK
Signal Description:
Transmit Channel Block
Signal Type:
Output
A user programmable output that can be forced high or low during any of the 32 E1 channels.
Synchronous with TCLK when the transmit side elastic store is disabled. Synchronous with TSYSCLK
when the transmit side elastic store is enabled. Useful for blocking clocks to a serial UART or LAPD
controller in applications where not all E1 channels are used such as Fractional E1, 384 Kbps (H0), 768
Kbps, 1920 bps (H12) or ISDN–PRI . Also useful for locating individual channels in drop–and–insert
applications, for external per–channel loopback, and for per–channel conditioning. See Section 16 for
details. This signal is not bonded out in the DS21FF44/DS21FT44.
Signal Name:
TSYSCLK
Signal Description:
Transmit System Clock
Signal Type:
Input
1.544 MHz or 2.048 MHz clock. Only used when the transmit side elastic store function is enabled.
Should be tied low in applications that do not use the transmit side elastic store. Can be burst at rates up
to 8.192 MHz. This pin is tied to the RSYSCLK signal in the DS21FF44/DS21FT44.
Signal Name:
TLCLK
Signal Description:
Transmit Link Clock
Signal Type:
Output
4 KHz to 20 KHz demand clock for the TLINK input. See Section 18 for details. This signal is not
bonded out in the DS21FF44/DS21FT44.