参数资料
型号: DS1963S
厂商: MAXIM INTEGRATED PRODUCTS INC
元件分类: Memory IC:Other
英文描述: SPECIALTY MEMORY CIRCUIT, MEDB2
封装: MICROCAN-2
文件页数: 11/37页
文件大小: 349K
代理商: DS1963S
DS1963S
19 of 37
authentication was successful. User- and host authentication, if implemented, prevents the use of a
DS1963S as a coprocessor device since it requires several steps to get the MATCH flag set.
After transmitting the command code the bus master selects a memory page and its secret by transmitting
a target address anywhere within the page. Next the master transmits the SHA Control byte, which is a
code for one of the six SHA functions that can be performed. Next the master receives a CRC over the
command code, address, and control byte. As the CRC is received and the control byte and address were
valid the SHA engine will start immediately and compute a message authentication code as described in
Figure 8. While the SHA computation takes place the master will read all 1’s. As the computation is
finished the pattern will change to alternating 0’s and 1’s. The master must read at least 8 bits of this
alternating pattern. Otherwise the device might not properly respond to a subsequent Reset Pulse. In case
of an invalid control byte or address the master will continue reading all 1’s until it issues a Reset Pulse.
The exact location of the various data segments as they enter the input buffer of the SHA engine is shown
in Table 2.
Compute SHA Functions Figure 8
SHA Engine computes
Message Authentication Code
of a NULL secret,
data of the selected page and
15 bytes of scratchpad data
SUCCESS
SHA Engine computes
Message Authentication Code
of secret of the selected page,
data of the selected page and
15 bytes of scratchpad data
SUCCESS
X = 0 ; HIDE = 1
CHLG = 0 ; AUTH = 0
T4:T0 = 00000b
N
From Compute SHA
Command (Figure 7)
0Fh
Compute 1st
Secret
?
N
F0h
Compute next
Secret
?
N
3Ch
Validate Data
Page
?
Continued
below
SHA Engine computes
Message Authentication Code
of secret of the selected page,
data of the selected page and
15 bytes of scratchpad data
HIDE = 1 ; CHLG = 0
AUTH = 0 ; MATCH = 0
M = 0 ; X = 0
HIDE = 1 ; CHLG = 0
AUTH = 0 ; MATCH = 0
M = 0 ; X = 0
M = MATCH
(TA1[7:6]
SEC#[2:1])
To Compute SHA Command (Figure 7)
Y
E4:E0 = 11111b
Read Authenticated Page and Compute Challenge allow the master to input a 3-byte “challenge” in the
computation via scratchpad locations 20 through 22. All other data is taken from the selected memory
page, associated secret, cycle counter, ROM Registration number and flags. With Compute First Secret
and Compute Next Secret the scratchpad locations 8 through 22 need to be filled with a partial secret
before the SHA computation takes place. A coprocessor device performing a Validate Data Page or Sign
Data Page command must have in scratchpad bytes 8 through 11 the (incremented) value of the cycle
counter of the selected memory page of the roaming device, and it must have in bytes 13 through 19 the
ROM Registration Number (without CRC), and in byte 12 the page number. A roaming device
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