CFA633-RDI-KU datasheet(68/86 Pages) CRYSTAIFONTZ

68 / 86 page

Crystalfontz America, Inc.

Data Sheet Release Date 2012/02/21

www.crystalfontz.com

CFA633-RDI-KU LCD Module (Hardware v2.0 / Firmware u2v1)

February 2012

Page 68

Write Scratchpad Command (quote from the Maxim/Dallas DS1963S Data Sheet)

Write Scratchpad Command [0Fh]

HIDE = 0, Target Address range 0000h to 01FFh only

After issuing the write scratchpad command, the master must first provide the 2–byte target address, followed

by the data to be written to the scratchpad. The data will be written to the scratchpad starting at the byte offset

(T4:T0). The ending offset (E4: E0) will be the byte offset at which the master stops writing data. Only full data

bytes are accepted. If the last data byte is incomplete its content will be ignored and the partial byte flag PF will

be set.

When executing the Write Scratchpad command the CRC generator inside the DS1963S (see Figure 12)

calculates a CRC of the entire data stream, starting at the command code and ending at the last data byte sent

by the master. This CRC is generated using the CRC16 polynomial by first clearing the CRC generator and

then shifting in the command code (0FH) of the Write Scratchpad command, the Target Addresses TA1 and

TA2 as supplied by the master and all the data bytes. The master may end the Write Scratchpad command at

any time. However, if the ending offset is 11111b, the master may send 16 read time slots and will receive the

CRC generated by the DS1963S.

Write 10 bytes of identifiable test data {0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88, 0x99, 0xAA} to the scratch pad

in location 0:0

Command:

20 = Arbitrary DOW transaction

Data sent:

\000\000\x0F\x00\x00\x11\x22\x33\x44\x55\x66\x77\x88\x99\xAA

Data received:

C=84(d=0):00

Use the Read Scratchpad Command [AAh] to read back the data.

Command:

20 = Arbitrary DOW transaction

Data sent:

\000\013\xAA

Data received:

C=84(d=0):00,00,09,11,22,33,44,55,66,77,88,99,AA,1E

Now write 10 bytes of identifiable test data {0x12, 0x23, 0x34, 0x45, 0x56, 0x67, 0x78, 0x89, 0x9A, 0xAB} to the scratch

pad in location 0:0x0A

Command:

20 = Arbitrary DOW transaction

Data sent:

\000\000\x0F\x0A\x00\x12\x23\x34\x45\x56\x67\x78\x89\x9A\xAB

Data received:

C=84(d=0):00

Use the Read Scratchpad Command [AAh] to read back the data.

Command:

20 = Arbitrary DOW transaction

Data sent:

\000\013\xAA

Data received:

C=84(d=0):00,02,09,12,23,34,45,56,67,78,89,9A,AB,62

Reading and writing to the scratch pad is the first step required to communicate with the DS1863S. In order to fully use

the DS1963S for a dongle application that securely protects your software from copying, become familiar with the SHA

algorithm as it applies to the SHA iButton by studying the Maxim/Dallas white papers and application notes listed above.

Then create a software application that implements the secure challenge/response protocol as outlined in the application

notes.

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