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SAA2032

Digital equalization for the tape drive processing of the DCC system

Philips Electronics 

Philips Semiconductors

Digital equalization for the tape

drive processing of the DCC system

Product specification

SAA2032

The following three signals are generated:

1. LABEL: label detection (HIGH if label is detected).

2. VIRGIN: virgin tape detection (HIGH if virgin tape

is detected).

3. AENV: alternating envelope (sliced envelope).

AENV, LABEL and VIRGIN are disabled in normal or off

modes. LABEL, VIRGIN and AENV are LOW.

AENV, LABEL and VIRGIN are enabled when the

SAA2032 is in search mode.

The device detects the envelope AENV of the auxiliary

track at search speeds between 3 and 50 times normal

speed. If AENV is continuously HIGH (label detection),

LABEL will be HIGH.

When AENV is continuously LOW (virgin tape detection)

VIRGIN will be HIGH.

Figures 6, 7 and 8 show the relationship between AENV,

VIRGIN and LABEL.

Labelled tape-speed calculation

When the DCC player is in its search mode, the tape

speed increases. LABEL information is encoded

throughout its length. To examine the length of a label, the

tape speed must be known. In search mode the SAA2032

assesses the speed of labelled tapes. The microcontroller

obtains this information via the LT-interface.

The speed information is encoded in 3 variables:

1. SVF Speed Validation Flag (HIGH if invalid).

2. SC (4..0) Speed counter.

3. SR (1..0) Speed Range.

Search speed = 2SR × 5--S--1--C-.--2-- x normal speed.





If SC = 0 then search speed > 51.2.

With SR = 0, 1, 2 or 3 and SC = 0 to 31.

If SVF = 1 then SR and SC values are invalid.

Appendix 1 gives a table of the search mode speed

control.

Microcontroller (LT) Interface

The SAA2032 is able to exchange information with the

microcontroller via the LT-interface. The microcontroller

performs as master, the SAA2032 as slave.

Figure 9 gives the operation of the LT-interface.

RDCLK

VIN

RDSYNC

CH7 AUX *** CH0 CH1 CH2 CH3 CH4 CH5 CH6 CH7 AUX *** CH0 CH1

MCD477

Fig.4 Signals on interface between Read Amplifier and SAA2032.

February 1995

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