PXN20RM Datasheet, PDF (335/1376 Pages) Freescale Semiconductor, Inc – PXN20 Microcontroller

Flash Memory Array and Control
Table 12-3. MCR Field Descriptions (continued)
Field
Description
ESUS
Erase Suspend. ESUS is used to indicate that the flash module is in erase suspend or in the process of entering a
suspend state. The module is in erase suspend when ESUS = 1 and DONE = 1. ESUS can be set high only when
ERS and EHV are high and PGM is low. A 0 to 1 transition of ESUS starts the sequence which sets DONE and
places the flash in erase suspend.
ESUS can be cleared only when DONE and EHV are high and PGM is low. A 1 to 0 transition of ESUS with EHV = 1
starts the sequence which clears DONE and returns the module to erase. The flash module cannot exit erase
suspend and clear DONE while EHV is low. ESUS is cleared on reset.
0 Erase sequence is not suspended.
1 Erase sequence is suspended.
EHV
Enable High Voltage. The EHV bit enables the flash module for a high voltage program/erase operation. EHV is
cleared on reset. EHV must be set after an interlock write to start a program/erase sequence. EHV may be set,
initiating a program/erase, after an interlock under one of the following conditions:
• Erase (ERS = 1, ESUS = 0).
• Program (ERS = 0, ESUS = 0, PGM = 1, PSUS = 0).
• Erase-suspended program (ERS = 1, ESUS = 1, PGM = 1, PSUS = 0).
If a program operation is to be initiated while an erase is suspended the user must clear EHV while in erase suspend
before setting PGM.
In normal operation, a 1 to 0 transition of EHV with DONE high, PSUS and ESUS low terminates the current
program/erase high voltage operation.
When an operation is aborted, there is a 1 to 0 transition of EHV with DONE low and the suspend bit for the current
program/erase sequence low. An abort causes the value of PEG to be cleared, indicating a failed program/erase;
address locations being operated on by the aborted operation contain indeterminate data after an abort.
A suspended operation cannot be aborted. EHV may be written during suspend. EHV must be high for the flash
module to exit suspend. EHV may not be written after a suspend bit is set high and before DONE transitions high.
EHV may not be set low after the current suspend bit is set low and before DONE transitions low.
0 Flash is not enabled to perform a high voltage operation.
1 Flash is enabled to perform a high voltage operation.
Note: Aborting a high voltage operation leaves FC addresses in an indeterminate data state. This may be
recovered by executing an erase on the affected blocks.
NOTE
The program and erase sequence of the flash may be suspended to allow
read and program access to the flash core. A suspend operation is initiated
by setting the Erase Suspend (ESUS) bit or Program Suspend (PSUS) bit in
the flash Module Configuration Register (MCR). Setting a suspend bit
causes the flash module to start the sequence, which places it in the
suspended state. The user must then wait until the MCR[DONE] bit is set
before a read or program to the flash is initiated, as the high voltage
operation needs to be complete to avoid errors. However, during normal
read to the same partition, following a suspend sequence, (setting MCR bit
and waiting for MCR[DONE] bit to be set) can result in read fails that will
return multiple bit ECC errors. The error is due to the MCR[DONE] bit
being set before the internal high voltage operation is complete.
Freescale Semiconductor
PXN20 Microcontroller Reference Manual, Rev. 1
12-9