SPM and Security Subsystem

FX651

© 1997 Consumer Microcircuits Limited

13

D/651/4

System Timings (See also Table 1 on next page)

(a) SPM (12kHz) channel. Toneburst and tonegaps less than the response and de-response

delays

are ignored.

(b) Security tone (18kHz) channel. The response and de-response times are short to enable the

device to recognise the short ON-OFF bursts (20ms each).

(c) Transmit Mode. TXOP is modulated by the NRZ DATA pin. An 18kHz toneburst represents logic

"0" and "no tone" represents logic "1". Data packets with symbol periods greater than or equal to

6ms can be transmitted.

Figure 3 System Timing Diagrams