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TC1784
Program Memory Unit (PMU)
User´s Manual
5-66
V1.1, 2011-05
PMU, V1.47
special 32-bit confirmation (lock-) code is written into the UCB0-page2. Only this
confirmation code enables the protection and thus the keywords. The confirmation write
operation to the second wordline of the User Configuration Block shall be executed only
after check of keyword-correctness (with command “Disable Read Protection” after next
reset). The confirmed state and thus the installation of protection is indicated with the
FSR-bit PROIN in Flash Status Register FSR and for read protection with bit RPROIN in
FSR. If read protection is not correctly confirmed and thus not enabled, the bits PROIN
and RPROIN in the FSR are not set. The configured read protection as fetched from
UCB0 is indicated in the protection configuration register PROCON0
1)
.
For safety of the information stored in the UCB pages, all keywords, lock bits and the
confirmation code are stored two-times in the two wordlines. In case of a disturbed
original data detected during rampup, its copy is used. Layout of the four UC pages
belonging to the user’s UC block is shown in
below, the command
“Write User Configuration Page” is described in
With the command sequence “Disable Read Protection” a short-term disablement of
read protection is provided. With this command, it is possible to disable the Flash
protection (latest until next reset) for user controlled erase and re-program operations as
well as for clearing of DCF and DDF control bits after external program execution. The
“Disable Read Protection” command sequence is a protected command, which is only
processed by the command state machine, if the included two passwords are identical
to the two keywords of user 0. The disabled state of read protection is controlled with the
FCON-bit RPA=’0’ and indicated in the Flash Status Register FSR with the RPRODIS bit
(see
). As long as read protection is disabled (and thus not active), the
FCON-bits DDF and DCF can be cleared.
Resumption of read protection after disablement is performed with the “Resume
Read/Write Protection” command. After execution of this single cycle command, read
protection (if installed) is again active, indicated by the FCON bit RPA=’1’.
Generally, Flash read protection will remain installed as long as it is confirmed (locked)
in the User Configuration Block 0. Erase of UC block and re-program of UC pages can
be performed up to 4 times. But note, after execution of the Erase UC block command
(which is protected and therefore requires the preceding disable command with the
user’s specific passwords), all keywords and all protection installations of user 0 are
erased; thus, the Flash is no more read protected (beginning with next reset) until re-
programming the UC pages. But the division and separation of the protection
configuration data and of the confirmation data into two different UCB-wordlines
guarantees, that a disturb of keywords can be discovered and corrected before the
protection is confirmed. For this reason, the command sequence “Disable Read
Protection” can also be used when protection is programmed (configured) but not
confirmed; wrong keywords are then indicated by the error flag PROER.
1) PROCON0.DFEXPRO is only set when in UCB0 the bits for RPRO and DFEXPRO are set to 1.
Содержание TC1784
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