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USER’S GUIDE
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blocks over which the CRC calculation is performed.
For example, if the nibble is set to 0001b, the CRC range
is from 0000 to 0FFFh. Once the LSB of the CRC regis-
ter is set, the loader “I” command will cause the CRC of
the specified block to be computed. The result is auto-
matically stored in the last two bytes of the specified
block. These bytes should not be used by the applica-
tion. This computation will be correct provided that the
CRC range is less than or equal to the partition if PM=0.
If PM=1, using 32K RAMs, the CRC range must be less
than or equal to the program range.
If CRC is enabled, the DS5001FP will automatically
invoke the Bootstrap Loader on either power–up or a
Watchdog timeout and the CRC check will be per-
formed. If an error is detected, the Bootstrap Loader will
wait for reloading. If there is no error, the application will
begin at address 0000h following a reset. Automatic
checking of the CRC can be disabled by writing a 0 to
the CRC register LSB. As mentioned above, this is
done using the “W” command in loader mode. The CRC
hardware uses registers 0C3h and 0C2h for most and
least significant byte intermediate storage. The
DS5002FP and DS2252T do not perform a CRC check
to ensure software security.
DS5001 CRC REGISTER (Address 0C1h)
RNGE3 RNGE2 RNGE1 RNGE0 ––– ––– MDM CRC
CRC.7–4: RANGE 3–0
Determines the range over which a power–up CRC will be performed.
Addresses are specified on 4K boundaries.
Initialization: Reset to 0 on a No V
LI
reset.
Read Access: Can be read at any time.
Write Access: Cannot be written by application software. Can be written via the Bootstrap
Loader.
CRC.1: MDM
When set to 1, the Bootstrap Loader will attempt to use a modem (UART)
on PE4 if CRC is incorrect. This feature is no longer useful following the
obsoletion of the corresponding modem devices.
Initialization: Reset to 0 on a No V
LI
reset.
Read Access: Can be read at any time.
Write Access: Cannot be written by application software. Can be written via the Bootstrap
Loader.
CRC.0: CRC
When set to 1, a CRC check will be performed on power–up or watchdog
timeout. CRC will be checked against stored values. An error will initiate
Program Load mode. This bit will not be present in the DS5002 as the device
does not support the power–on CRC function.
Initialization: Reset to 0 on a No V
LI
reset.
Read Access: Can be read at any time.
Write Access: Cannot be written by application software. Can be written via the Bootstrap
Loader.