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MCRF450 Datasheet PDF : 50 Pages
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MCRF450/451/452/455
6.2.3.3 Usage Of TSMAX And TCMAX
The parameters of TSMAX and TCMAX are
determined by an expected number of tags in the
Detection Loop. The following table shows the
EQUATION 6-1: COMMAND REPEAT TIME
Command Repeat Time = TSMAX × TCMAX × 2.5ms × 1.17
Where:
1.17 is related to the tolerance of the baud rate.
recommended FRR command repeat times for each of
the 7 possible combinations of TSMAX and TCMAX.
The command repeat time in Table 6-8 is calculated by:
TABLE 6-8: FRR COMMAND REPEAT TIME VS. (TSMAX, TCMAX)
(TSMAX, TCMAX)
(1,1)
(1,2)
(1,4)
(16,1)
(16,2)
Command Repeat Time 2.925 ms 5.85 ms 11.7 ms 46.8 ms 93.6 ms
(16,4)
187.2 ms
(64,1)
187.2 ms
6.2.3.4 1-of-16 PPM
The Interrogator uses 1-of-16 Pulse Position
Modulation (PPM) for MC1 and MC2 matching codes,
End Process (EP) and also commands in Table 6-2.
1-of-16 PPM uses only one gap pulse in one of
sixteen possible pulse positions for sending 4-bit
symbols (24 = 16). This means one symbol (one
data packet) represents 4 bits of binary data. One
symbol lasts for 2.8 ms and 160 µs for Normal Speed
and Fast Speed mode, respectively. All communica-
tions begin with time calibration pulses (TCP)
composed of three pulses in positions, zero, six and
fourteen of a 1-of-16 PPM symbol, as shown in
Figure 6-10.
TABLE 6-9: 1-OF-16 PPM PULSE SPECIFICATIONS
Normal Mode
Modulation depth (MODINDEX_GAP)
Pulse width
Gap width
Pulse positions per symbol
Symbol width
Calibration sequence
100% (max)
175 µs (typical)
100 µs (typical)
16
2.8 ms (typical)
Pulses in positions 0, 6, 14
Fast Mode
100% (max)
10 µs (typical)
7 µs (typical)
16
160 µs (typical)
Pulses in positions 0, 6, 14
DS40232H-page 28
2003 Microchip Technology Inc.
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