Rainbow Electronics MAX66020 - Manual (Page 18)

MAX66020
ISO/IEC 14443 Type B-Compliant
1Kb Memory Fob
18 ______________________________________________________________________________________
Network Function Commands
To transition slaves devices between states, the
ISO/IEC 14443 Type B standard defines six network
function commands, called REQB, WUPB, SLOT-
MARKER, HLTB, ATTRIB, and DESELECT. The master
issues the commands in the form of request frames and
the slaves respond by transmitting response frames.
With network function commands, command code,
parameters and response are embedded between SOF
and CRC. This section describes the format of the
response and request frames and the coding of the
data fields inside the frames as detailed as necessary
to operate the MAX66020. Not all of the fields and
cases that the standard defines are relevant for the
MAX66020. For a full description of those fields refer to
the ISO/IEC 14443-3, Section 7.
REQB/WUPB Command
The REQUEST command, Type B (REQB) and the
WAKEUP command, Type B (WUPB) are the general
tools for the master to probe the RF field for the presence
of slave devices and to preselect them for action based
on the value of the application family identifier (AFI). An
ISO/IEC 14443 Type B-compliant slave watches for these
commands while in the IDLE state, WAITING FOR SLOT-
MARKER state, and READY state. In the HALT state, the
slave only acts upon receiving a WUPB command. The
REQB or WUPB command is transmitted as a frame, as
shown in Figure 18. Besides the command code, the
request includes two parameters, AFI and PARAM. The
response to REQB/WUPB is named ATQB. See the
ATQB Response section for details.
The ISO/IEC 14443 standard defines rules for the
assignment of the AFI codes and the behavior of the
slaves when receiving a REQB/WUPB request. If the
request specifies an AFI of 00h, a slave must process
the command regardless of its actual AFI value. If the
least significant nibble of the AFI in the request is
0000b, the slave must process the command only if the
most significant nibble of the AFI sent by the master
matches the most significant nibble of the slave’s AFI.
For all other AFI values, the slave processes the com-
mand only if the AFI in the request and the slave match.
The AFI code can be programmed and locked by the
user. For details see the
Memory and Control Function
Commands section.
The bit assignments of the PARAM byte are shown in
Figure 19. Bits 5 to 8 are reserved and must be trans-
mitted as 0. Bit 4, if 0, indicates that the request is a
REQB command; bit 4, if 1, defines a WUPB command.
Bits 1, 2, and 3 specify the number of slots (N) to be
used in the anticollision protocol. Table 6 shows the
codes. In the case of N = 1, the SLOT-MARKER com-
mand does not apply and all slaves with a matching AFI
transition to the READY state. With multiple slaves in the
field, this leads to a data collision, since the response
frames are transmitted simultaneously. If N is 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
COMMAND SOF AFI CRC PARAM EOF
05h (1 BYTE) (2 BYTES) (1 BYTE)
Figure 18. REQB/WUPB Request Frame
BIT 8 BIT 7 BIT 6 BIT 5 BIT 4
REQB/
WUPB
BIT 3 BIT 2 BIT 1
MSb LSb
0 0 0 0
(FIXED) N
Figure 19. Bit Assignments for PARAM Byte
BIT 3 BIT 2 BIT 1 N
0 0 0 1
0 0 1 2
0 1 0 4
0 1 1 8
1 0 0 16
1 0 1 (RESERVED)
1 1 X (RESERVED)
Table 6. Number of Slots Codes