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GUIDELINES FOR MIGRATING ST72C254 APPLICATIONS TO ST72F264

6 OPTION BYTES

Option bits have been added, split or replaced in the ST72F264 compared to the ST72C254

(see Figure 7.):

s

Oscillator type bits have been added in order to select a best range of backup safe oscillator

s

CFC (Clock Filter Control) bit has been removed

s

FMP (Full Memory Protection) bit has been split into 2 bits: FMP_R (read protection) and

FMP_W (write protection)

s

SEC[1:0] bits have been added to select the ST72F264 sector 0 size

s

PLL selection bit has been added

s

External RC clock option is no longer supported with ST72F264 device.

For more information concerning these option bits, please refer to the datasheet.

Figure 7. ST72C254 and ST72F264 Option Bytes

s

LVD low and high configuration levels have been swapped:

USER OPTION BYTE 1

15

8

USER OPTION BYTE 0

70

EXTIT

1

OSC

TYPE

1

OSC

TYPE

0

OSC

RNGE

2

OSC

RNGE

1

OSC

RNGE

0

PLL

OFF

WDG

HALT

WDG

SW

VD1

VD0

SEC1

SEC0 FMPR FMPW

USER OPTION BYTE 0

70

USER OPTION BYTE 1

70

EXTIT

FMP

CFC

OSC2 OSC1 OSC0

LVD1

LVD0

WDG

HALT

WDG

SW

ST72C254 Option Bytes

Reserved

ST72F264 Option Bytes