
DS2490
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WRITE EPROM—This command is used to write data directly to the data or status memory of a 1-Wire
EPROM device. If embedded command bit DT = 1, the CRC16 generator is selected; if DT = 0, CRC8 is
used. Embedded command bit Z controls the method used for comparison of the data written to the 1-
Wire device. Additionally, embedded command bit F can be used to clear the Communication command
buffer and EP2/3 FIFOs if an error occurs during execution of the command. The EP2 FIFO must be pre-
filled with preamble and EPROM data before command execution. Additionally, for data block sizes
greater then the EP2 FIFO size, the FIFO content status must be monitored by host SW so that additional
data can be sent to the FIFO when necessary.
Command parameters:
2 bytes specifying block size.
EP2 data:
Length
3-bytes +
block size
Preamble and data bytes to be sent to the 1-Wire
EPROM device. 3-byte preamble: 1-Wire command
code, TA1, TA2 (typical).
EP3 data:
None
Result Register:
Code
Condition
CRC, CMP,
VPP
ICP = 0, NTF = 0 or 1: and an error condition.
0x00
ICP = 0, NTF = 1: no error detected
None
ICP = 0, NTF = 0: no error detected
None
ICP = 1
READ CRC PROT PAGE—This command is used to read one or multiple CRC-protected pages of
EPROM devices and to read tamper-detect bytes and counter value of Monetary iButtons. If embedded
command bit DT = 1, the CRC16 generator is selected; if DT = 0, CRC8 is used. Embedded command bit
CIB is used to specify either a 2- or 3-byte read preamble. Additionally, embedded command bit F can be
used to clear the Communication command buffer and EP2/3 FIFOs if an error occurs during execution
of the command. The command can also be used to read a single partial page up to the end of that page
and reading the PIOs of a DS2406. This command is also applicable to the Read IPR function of the
crypto iButton if CIB = 1. The EP2 FIFO must be pre-filled with preamble data before command
execution. To prevent overflow, the EP3 FIFO must be monitored (and read if necessary) during
command execution if reading more data than the size of the EP3 FIFO.