ST7232A datasheet(146/157 Pages) STMICROELECTRONICS

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ST7232A

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ST7232A DEVICE CONFIGURATION AND ORDERING INFORMATION (Cont’d)

OPTION BYTE 1

OPT7= PKG1 Pin package selection bit

This option bit selects the package.

Note: On the chip, each I/O port has 8 pads. Pads

that are not bonded to external pins are in input

pull-up configuration after reset. The configuration

of these pads must be kept at reset state to avoid

added current consumption.

OPT6 = RSTC RESET clock cycle selection

This option bit selects the number of CPU cycles

applied during the RESET phase and when exiting

HALT mode. For resonator oscillators, it is advised

to select 4096 due to the long crystal stabilization

time.

0: Reset phase with 4096 CPU cycles

1: Reset phase with 256 CPU cycles

OPT5:4 = OSCTYPE[1:0] Oscillator Type

These option bits select the ST7 main clock

source type.

OPT3:1 = OSCRANGE[2:0] Oscillator range

When the resonator oscillator type is selected,

these option bits select the resonator oscillator

current source corresponding to the frequency

range of the used resonator. Otherwise, these bits

are used to select the normal operating frequency

range.

OPT0 = PLL OFF PLL activation

This option bit activates the PLL which allows mul-

tiplication by two of the main input clock frequency.

The PLL is guaranteed only with an input frequen-

cy between 2 and 4MHz.

0: PLL x2 enabled

1: PLL x2 disabled

CAUTION: the PLL can be enabled only if the

“OSC RANGE” (OPT3:1) bits are configured to

“MP - 2~4MHz”. Otherwise, the device functionali-

ty is not guaranteed.

Version

Selected Package

PKG1

TQFP32 / SDIP32

TQFP44 / SDIP42

Clock Source

OSCTYPE

Resonator Oscillator

Reserved

External Source

Typ. Freq. Range

OSCRANGE

210

1~2MHz

2~4MHz

4~8MHz

8~16MHz

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