TCM29C13 Datasheet, PDF (20/25 Pages) Texas Instruments – COMBINED SINGLE-CHIP PCM CODEC AND FILTER

TCM29C13, TCM29C14, TCM29C16, TCM29C17,
TCM129C13, TCM129C14, TCM129C16, TCM129C17
COMBINED SINGLE-CHIP PCM CODEC AND FILTER
SCTS011H – APRIL 1986 – REVISED JULY 1996
PRINCIPLES OF OPERATION
variable-data-rate timing
Variable-data-rate timing is selected by connecting DCLKR to the bit clock for the receive PCM highway rather
than to V_BB. It uses master clocks CLKX and CLKR, bit clocks DCLKX and DCLKR, and frame-synchronization
clocks FSX and FSR.
Variable-data-rate timing allows for a flexible data frequency. The frequency of the bit clocks can be varied from
64 kHz to 2.048 MHz. Master clocks in the TCM29C13, TCM29C14, TCM129C13, and TCM129C14 are
restricted to frequencies of operation of 1.536 MHz, 1.544 MHz, or 2.048 MHz as in the fixed-data-rate timing
mode. The master clock for the TCM29C16, TCM29C17, TCM129C16, and TCM129C17 is restricted to 2.048
MHz.
When the FSX/TSXE is high, PCM data is transmitted from PCM OUT onto the highway on the next eight
consecutive positive transitions of DCLKX. Similarly, while the FSR/TSRE input is high, the PCM word is
received from the highway by PCM IN on the next eight consecutive negative transitions of DCLKR.
The transmitted PCM word is repeated in all remaining time slots in the 125-µs frame as long as DCLKX is pulsed
and FSX is held high. This feature, which allows the PCM word to be transmitted to the PCM highway more than
once per frame if desired, is available only with variable-data-rate timing. Signaling is allowed only in the
fixed-data-rate mode because the variable-data-rate mode provides no means with which to specify a signaling
frame.
signaling
The TCM29C14 (only) provides 8th-bit signaling in the fixed-data-rate timing mode. Transmit and receive
signaling frames are independent of each other and are selected by a double-width frame-sync pulse on the
appropriate channel. During a transmit signaling frame, the signal present on SIGX is substituted for the least
significant bit (LSB) of the encoded PCM word. In a receive signaling frame, the codec decodes the seven most
significant bits in accordance with CCITT G.733 recommendations and outputs the logical state of the LSB on
SIGR until it is updated in the next signaling frame. Timing relationships for signaling operations are shown in
Figure 8. The signaling path is used to transmit digital signaling information such as ring control, rotary dial
pulses, and off-hook and disconnect supervision. The voice path is used to transmit prerecorded messages as
well as the call progress tones: dial tone, ring-back tone, busy tone, and reorder tone.
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