TC1784
Program Memory Unit (PMU)
User´s Manual
5-61
V1.1, 2011-05
PMU, V1.47
After an erase operation, a correct ECC code (all zero) is provided for the erased sector
in the Program Flash as well as in the Data Flash.
For details about handling ECC errors and other flags see
5.6.4.2
Margin Check Control
Margin control is supported for the sense amplifiers separately of the Program Flash and
the Data Flash. With the two margin control registers MARP (for Program Flash) and
MARD (for Data Flash) the sensing of array bit lines can be controlled more critical for
‘0’ or ‘1’ values during read operations. The Margin Control Registers MARP and MARD
are used to change the margin levels for read operations to find problematic array bits.
Since problematic bits always change their value from ‘1’ to ‘0’, it is quite simple to find
those bits: The array area to be checked is read with changed margins which are more
critical for sensing ‘1’ values (verify operation). A single or double-bit error will be
reported to the CPU by an error interrupt or a bus error trap. The double-bit error trap
can be disabled for margin checks and also redirected to an error interrupt.
The different margin levels are enabled and selected with the Margin Control Registers
MARP and MARD. The high margin levels which can be selected, are one low level
margin (coded with ‘0’) and one high level margin (coded with ‘1’).
Note: Only one margin change (high or low level, PFlash or DFlash) is allowed at a time.
Note: To increase the security and to inhibit unintended write accesses, the standard
“ENDINIT” protection feature (including watchdog password access control) is
used for write accesses to the margin control register MARP (for Program Flash).
The MARD register for Data Flash is
not
especially protected.
Note: After change of margin level, a wait time of >10µsec. for sense amp adjustment is
necessary before read operations with the modified margins shall be executed.
Note: During erase or program operation only the standard (default) margins are allowed
(no margin change for parallel read accesses).
Note: Although double-bit error traps are disabled with reset, the traps are enabled by
the startup SW (firmware) in Boot ROM before Boot ROM exit.
The Margin Control Registers for Program Flash (MARP) and for Data Flash (MARD)
are defined as follows:
Summary of Contents for TC1784
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