Mask Set Errata for 9S08QG8, Mask 3M77B

2

Freescale Semiconductor

Workaround

This problem applies to the non-interrupt functions that are shared with IRQ and KBI functions. Because

interrupts from IRQ or KBI are disabled, these pins are not used to wake up the MCU from stop. To

prevent signals on IRQ or KBI from causing an unexpected partial wakeup from stop in these applications,

disable the IRQ and KBI modules just before entering stop mode. Also verify that any previous interrupt

flags associated with IRQ and KBI have been cleared.

Unexpected Flash Block Protection Errors

SE133-FLASH

Description

If a portion of the nonvolatile memory (NVM) is block protected, unexpected flash block protect violation

(FPVIOL) errors can result. These errors can occur during an attempt to program or erase locations in

areas of the NVM that are not block protected. Software methods can be used to avoid this potential

problem. The problem is more likely to be seen on devices that have multiple nonvolatile blocks, including

devices with two or more separate flash blocks or with flash plus EEPROM. If block protection is not

enabled, no errors occur.

This error is related to logic that compares current block protection settings to an internally latched

address. This internal address is written (latched) at reset, at the end of most flash commands, and

whenever there is a write to a location in NVM. If a read access to the partially protected NVM is

performed immediately before the write to unprotected memory that starts a new flash command, the

erroneous address that was previously in the internal latch can cause a false indication of a protection

violation. A short sequence of instructions can be performed before starting normal flash commands to

ensure that the address in the internal latch is not a protected address.

Workarounds

The preferred workaround starts a command to a known unprotected address (which internally latches

the known-unprotected address), forces an access error to abort that command, and then clears the

resulting error flags before starting any new flash command. This workaround assumes the H:X index

register points to the location or sector you want to program or erase, and accumulator A has the data

value you plan to write to that location. Start your program or erase routine with the following instructions.

STA

,X

;latch the unprotected address from H:X

NOP

;brief delay to allow the command state machine to start

STA

,X

;intentionally cause an access error to abort this command

PSHA

;temporarily save data value

LDA

#$30

;1’s in PVIOL and ACCERR bit positions

STA

FSTAT

;clear any error flags

PULA

;restore data value

STA

,X

;STEP 1 write data to start new command