DS2175

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SLIP CORRECTION CAPABILITY

The 2–frame buffer depth is adequate for T–carrier and CEPT applications where short term jitter

synchronization, rather than correction of significant frequency differences, is required. The DS2175

provides an ideal balance between total delay (less than 250 microse-conds at its full depth) and slip

correction capability.

BUFFER RECENTERING

Many applications require that the buffer be recentered during system power–up and/or initialization.

Forcing

ALN low recenters the buffer on the occurrence of the next frame sync boundary. A slip will

occur during this recentering if the buffer depth is adjusted. If the depth is presently optimum, no

adjustment (slip) occurs.

SLIP REPORTING

SLIP is held low for 65 SYSCLK cycles when a slip occurs. SLIP is an active–low, open collector

output. FSD indicates slip direction. When low (buffer empty) a frame of data was “repeated” at SSER

during the previous slip. When high (buffer full), a frame of data was “deleted”. FSD is updated at every

slip occurrence.

BUFFER DEPTH MONITORING

SMSYNC is a system side output pulse which indicates system side multiframe boundaries. The distance

between rising edges of RMSYNC and SMSYNC indicates the current buffer depth. Impending slip

conditions may be determined by monitoring RMSYNC and SMSYNC real time. SMSYNC is held high

for 65 SYSCLK periods.

CLOCK SELECT

Receive and system side clock frequencies are independently selectable by inputs RCLKSEL and

SCLKSEL. 1.544 MHz is selected when RCLKSEL (SCLKSEL) = 0; 2.048 MHz is selected when

RCLKSEL (SCLKSEL) = 1. In 1.544 MHz (receive) to 1.544 MHz (system) applications, the F-bit

position is passed through the receive buffer and presented at SSER immediately after the rising edge of

the system side frame sync. The F–bit position is forced to 1 in 2.048 MHz to 1.544 MHz applications.

No F–bit position exists in 2.048 MHz system side applications.

PARALLEL COMPATIBILITY

The DS2175 is compatible with parallel and serial backplanes. Channel 1 data appears at SSER after a

a parallel format requires an HC595 shift register.