EM4170
Authentication
In this mode the chip first receives the 56 bits of random number followed by a certain number of divergency bits that the
reader should send as "0" followed by 28 Bits of cipher_1 (f(RN)) as authentication of the lock. The chip decides if the
authentication is accepted. In this case the EM4170 sends a header (12 Manchester coded '1's followed by 4 Manchester
coded '0's). Next 20 Bits of cipher_2 (g(RN)) are sent. Else it sends a single NAK. Upon completion of this command the
EM4170 returns to Standby Mode.
Begin
Receive
RN
f(RN)
(56 Bits)
valid?
Y
N
Divergency
Send
Send
NAK
header
Receive
f(RN)
(28 Bits)
Send
g(RN)
(20 Bits)
End
Fig. 7
Tauth
Tdiv
OUTPUT
INPUT
LIW
RM
Header
g(RN)
LIW
Command
RN
“0000000”
f(RN)
Fig. 8
Write Word
The Write Word command is followed by the address and data. The address consists of a 5 bit block containing 4 data bits
and 1 even parity. The data consists of 4 times 5 bit blocks, each block consisting of 4 data bits and 1 associated even
parity bit. One additional block consists of 4 column parity bits and a trailing zero (refer to fig 10).
Address
A3 A2 A1 A0 Padd
First bit received
Data
D15 D14 D13 D12 P3 D11 D10 D09 D07 P2 D07 D06 D05 D04 P1 D03 D02 D01 D00 P0 PC3 PC2 CP1 PC0 "0"
Fig. 9
7
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