ST72321 datasheet(172/185 Pages) STMICROELECTRONICS

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ST72321

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14 ST72321 DEVICE CONFIGURATION AND ORDERING INFORMATION

Each device is available for production in user pro-

grammable versions (FLASH) as well as in factory

coded versions (ROM/FASTROM).

ST72321 devices are ROM versions. ST72P321

devices are Factory Advanced Service Technique

ROM (FASTROM) versions: they are factory-pro-

grammed HDFlash devices. Each device is availa-

ble for production in user programmable versions

(FLASH) as well as in factory coded versions

(ROM). FLASH devices are shipped to customers

with a default content, while ROM/FASTROM fac-

tory coded parts contain the code supplied by the

customer. This implies that FLASH devices have

to be configured by the customer using the Option

Bytes while the ROM/FASTROM devices are fac-

tory-configured.

14.1 FLASH OPTION BYTES

The option bytes allow the hardware configuration

of the microcontroller to be selected. They have no

address in the memory map and can be accessed

only in programming mode (for example using a

standard ST7 programming tool). The default con-

tent of the FLASH is fixed to FFh. To program the

FLASH devices directly using ICP, FLASH devices

are shipped to customers with the internal RC

clock source enabled. In masked ROM devices,

the option bytes are fixed in hardware by the ROM

code (see option list).

OPTION BYTE 0

OPT7= WDG HALT

Watchdog and HALT mode

This option bit determines if a RESET is generated

when entering HALT mode while the Watchdog is

active.

0: No Reset generation when entering Halt mode

1: Reset generation when entering Halt mode

OPT6= WDG SW

Hardware or software watchdog

This option bit selects the watchdog type.

0: Hardware (watchdog always enabled)

1: Software (watchdog to be enabled by software)

OPT5 = CSS

Clock security system on/off

This option bit enables or disables the clock secu-

rity system function (CSS) which includes the

clock filter and the backup safe oscillator.

0: CSS enabled

1: CSS disabled

Caution: The CSS function is not guaranteed. Re-

fer to Section 15

OPT4:3= VD[1:0]

Voltage detection

These option bits enable the voltage detection

block (LVD, and AVD) with a selected threshold for

the LVD and AVD (EVD+AVD).

Caution: If the medium or low thresholds are se-

lected, the detection may occur outside the speci-

fied operating voltage range. Below 3.8V, device

operation is not guaranteed. For details on the

AVD and LVD threshold levels refer to Section

12.3.2 on page 139

OPT2 = Reserved, must be kept at default value.

OPT1= PKG0

Package selection bit 0

This option bit is used to select the package (see

table in PKG1 option bit description).

STATIC OPTION BYTE 0

STATIC OPTION BYTE 1

WDG

OSCTYPE

OSCRANGE

Default

11100

Selected Low Voltage Detector

VD1

VD0

LVD and AVD Off

Lowest Threshold: (VDD~3V)

Med. Threshold (VDD~3.5V)

Highest Threshold (VDD~4V)

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