Maxim Integrated MAXQ622 - Manual (Page 131)

MAXQ612/MAXQ622 User’s Guide
Maxim Integrated 8-7
Figure 8-6. Receive Burst-Count Example
IRRX
1 2 3
5
6 8 4 7
CARRIER FREQUENCY
CALCULATION
IRMT = PULSE COUNTING IRMT = PULSE COUNTING
IRV
IRMT
IRV = CARRIER CYCLE COUNTING
9
0
CAPTURE INTERRUPT (IRIF = 1)
IRV
≥ IRMT
IRV = 0 (IF IRXRL = 1)
TO 0 4
SOFTWARE SET IRCA = CARRIER FREQUENCY.
SOFTWARE SETS RXBCNT = 1 (WHICH SETS IRMT = 0001 IN HARDWARE).
SOFTWARE CLEARS IRCFME = 0 SO THAT IRV COUNTS CARRIER CYCLES. IRV IS RESET TO 0 ON QUALIFIED EDGE DETECTION IF IRXRL = 1.
SOFTWARE ADDS TO IRMT THE NUMBER OF PULSES USED FOR CARRIER MEASUREMENT.
IRCA x 2X COUNTER FOR SPACE CAN BEGIN IMMEDIATELY (QUALIFIED EDGE WILL RESET) .
5
QUALIFIED EDGE DETECTED: IRMT++
IRV RESET TO 0 IF IRXRL = 1.
6
IRCA x 2 PERIOD ELAPSES: IRIF = 1; CARRIER ABSENCE = SPACE.
BURST MARK = IRMT PULSES.
SOFTWARE CLEARS RXBCNT = 0 SO THAT WE CAPTURE ON THE NEXT QUALIFIED EDGE.
7
QUALIFIED EDGE DETECTED: IRIF = 1, CAPTURE ≥ IRMT AS THE BURST SPACE (PLUS UP TO ONE CARRIER CYCLE). 8
SOFTWARE SET RXBCNT = 1 AS IN (5).
CONTINUE (5) TO (8) UNTIL LEARNING SPACE EXCEEDS SOME DURATION. IRV ROLLOVERS CAN BE USED.
9