Rainbow Electronics MAX66000 - Manual (Page 13)

MAX66000
ISO/IEC 14443 Type B-Compliant
64-Bit UID
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larger than 1, each slave in the field selects its own
4-bit random number, R, in the range of 1 to N. A slave
that happens to choose R = 1 responds to the
REQB/WUPB request. The larger N is the lower the
probability of colliding response frames; however, if N
is 16 and there is only a single slave in the field, it can
take up to 15 SLOT-MARKER commands to get a
response. The method to identify all slaves in the field
relying solely on the random number R and the
REQB/WUPB command is called the “probabilistic
approach.” For mode information about the anticollision
process, see the
Anticollision Examples section.
SLOT-MARKER Command
Instead of relying on the fact that a participating slave
chooses a new random number for every REQB/WUPB
command, in the “time-slot approach” the master calls
the slaves by their random number R using the SLOT-
MARKER command. Before this can be done, the mas-
ter must have issued the REQB/WUPB command with a
number of slots (N) value greater than 1. The master
can send up to (N - 1) SLOT-MARKER commands.
Figure 19 shows the format of the SLOT-MARKER
request frame. The AFI field is not needed since the
slaves have already been preselected through the pre-
ceding REQB/WUPB request. The response to the
SLOT-MARKER command is called ATQB. See the
ATQB Response section for details.
The bits marked as “nnnn” specify the slot number as
defined in the Table 3. Any sequence of the permissible
slot numbers is permitted.
ATQB Response
The response for both the REQB/WUPB and the SLOT-
MARKER command is called ATQB, which stands for
“answer to request, Type B.” Figure 20 shows the for-
mat of the ATQB response. The PUPI field (pseudo-
unique identifier) is used by the master to address a
slave for transitioning to the ACTIVE or HALT state. The
data reported as PUPI is the least significant 4 bytes of
the 64-bit UID. The application data field reports user-
defined data that is relevant for distinguishing otherwise
equal slaves in the RF field. The application data field is
factory programmed to reflect the most significant 4
bytes of the 64-bit UID. This allows the master to obtain
the full 64-bit UID in the first response from the slave.
However, this field may be factory-programmed to a
customer-specific value.
The protocol info field provides the master with admin-
istrative information, such as data rate, frame size,
ISO/IEC 14443-4 compliance, frame waiting time, and
whether the slave supports CID and NAD in the
ISO/IEC 14443-4 block transmission protocol. Figure 21
shows where this information is located in the protocol
info field and what the values are.
COMMAND SOF CRC EOF
nnnn0101b (2 BYTES)
Figure 19. SLOT-MARKER Request Frame
INDICATOR SOF CRC EOF
50h
APPLICATION DATA
(4 BYTES) (2 BYTES)
PROTOCOL INFO
(3 BYTES)
PUPI
(4 BYTES)
Figure 20. ATQB Response Frame
BIT 8 BIT 7 BIT 6 BIT 5 SLOT NUMBER
0 0 0 1 2
0 0 1 0 3
0 0 1 1 4
… … … … …
1 1 1 0 15
1 1 1 1 16
Table 3. Slot Numbering