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TM-75/76 External Signals

TM-75/76 High-Resolution CCD Camera

4 TM-75/76 External Signals

This section explains how the external signals (HD and VD) and shutter trigger signal (TRIG) must be

fed in External sync (HD, VD sync) and Reset-Restart operation.

4.1 External HD

When external HD is supplied to pin #6 of the 12-pin connector, the TM-75/76 automatically switches

the clock to phase-lock to the external clock via HD PLL (phase lock loop). The PLL detects the leading

edge of external HD and Phase compare with the internal HD. Then PLL circuit generates internal clock

to phase-lock with the external clock. Therefore, the leading edges of both external and internal HD are

in exactly the same position. The PLL capture range is ±5% of fHD (=15.734KHz: EIA, 15.625: CCIR).

It is, however, advisable to stay within ±1% of fHD frequency to assure the best PLL jitter

characteristics. Without the presence of external HD, the TM-75/76 maintains the internal sync. The

input impedance of external HD and VD is 75Ω at factory set. A high-impedance option is also

available.

4.2 External VD

The TM-75/76 interface circuit deliberately delays external VD by two pixel clock (14 nsec) to ensure

the stable reset of VD in relation to external HD.

FIGURE 4. External Vd Delay Timing

For HD, VD external sync operation, apply VD to pin #7 of the 12-pin connector. The input impedance

is 75Ω. The VD reset range is from 244H to 1023.5H. For normal RS-170 operation, the VD must be

interlace scan at 262.5H (59.94 Hz = 16.7 msec). At 525H, it generates one full frame timing. The

integer (i.e. 262) reset makes non-interlace sync operation. Half H number (i.e. 262.5) makes interlace

scanning.

Note: The TM-76 vertical scan is 625H. VD is deﬁned as 312.5H (50Hz).

4.3 Reset-Restart VD

For Reset-Restart VD operation, VD is asynchronous in relation to any previous VD. Depending on

ﬁeld or frame mode, however, once the ﬁrst VD is asynchronously set, consecutive VD must be

generated to obtain proper images. I n general, the ﬁrst ﬁeld in ﬁeld mode or the ﬁrst frame in frame

mode is not usable because they are previous images prior to reset. A frame grabber has to know which

frame or ﬁeld to capture. External HD must be applied for this operation.

EXT HD

EXT VD (R.R.)

Internal VD

Two-pixel delay

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Pulnix TM-76 Manual de instrucciones Pagina 19