Rainbow Electronics MAX66100 User Manual

Page 4

MAX66100

distinct from any 2-bit pattern. The position of the sec-
ond notch tells whether the frame uses the “1 out of
256” or “1 out of 4” coding scheme (Figures 8 and 9,
respectively). The transmission of the EOF pattern
takes 37.76µs; the EOF is the same for both coding
schemes and has one modulation notch (Figure 10).

The path from slave to master uses one or two subcar-
riers, as specified by the Subcarrier_flag bit in the
request data packet. The standard defines two data
rates for the response, low (approximately 6600bps)

and high (approximately 26,500bps). The Data_rate_flag
bit in the request data packet specifies the response
data rate. The data rate varies slightly depending on the
use of one or two subcarriers. The LSb is transmitted
first. A compliant device must support both subcarrier
modes and data rates.

In the single subcarrier case, the subcarrier frequency
is 423.75kHz. One bit is transmitted in 37.76µs (high
data rate) or 151µs (low data rate). The modulation is
the on/off key. For a logic 0, the subcarrier is on during
the first half of the bit transmission time and off for the
second half. For a logic 1, the subcarrier is off during
the first half of the bit transmission time and on for the
second half. See Figure 11 for more details.

In the two subcarrier cases, the subcarrier frequencies
are 423.75kHz and 484.28kHz. The bit duration is the
same as in the single subcarrier case. The modulation
is equivalent to binary FM. For a logic 0, the lower sub-
carrier is on during the first half of the bit transmission
time, switching to the higher subcarrier for the second
half. For a logic 1, the higher subcarrier is on during the
first half of the bit transmission time, switching to the
lower subcarrier for the second half. See Figure 12 for
details. The transmission of the SOF pattern takes the
same time as transmitting 4 bits (approximately 151µs
at a high data rate or approximately 604µs at a low data
rate). The SOF is distinct from any 4-bit data sequence.
The EOF pattern is equivalent to a SOF being transmit-
ted backwards. The exact duration of the SOF and EOF
varies slightly depending on the use of one or two sub-
carriers (see Figures 13 and 14, respectively).

ISO 15693-Compliant 64-Bit UID

_______________________________________________________________________________________

Figure 5. Downlink Modulation (e.g., Approximately 100%
Amplitude Modulation)

CARRIER

AMPLITUDE

100%

Figure 6. Downlink Data Coding (Case “1 Out of 256”)

PULSE-

MODULATED

CARRIER

2
2
5

2
5
2

2
5
3

2
5
4

2
5
5

~ 9.44

μs

~ 18.88

μs

~ 4.833ms