ST72F321J ST Microelectronics, ST72F321J Datasheet - Page 170

• Manufacturer Part Number: ST72F321J
• Description: 8-BIT MCU
• Manufacturer: ST Microelectronics

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DataSheet
ST72321J
ST72321J DEVICE CONFIGURATION AND ORDERING INFORMATION (Cont’d)
OPTION BYTE 1
OPT7= PKG1 Package selection bit 1
This option bit with the PKG0 bit, selects the 44 pin
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
Note: when the CSS is enabled, the device starts
to count immediately thanks to the backup oscilla-
tor.
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
170/179
Resonator Oscillator
External RC Oscillator
Internal RC Oscillator
External Source
Version
4
J
U
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Clock Source
Selected Package
TQFP44
1
0
0
1
1
OSCTYPE
PK1
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0
PKG0
0
0
1
0
1
0
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 must not be used with the internal RC os-
cillator. The PLL is guaranteed only with an input
frequency 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.
LP
MP
MS
HS
Typ. Freq. Range
8~16MHz
1~2MHz
2~4MHz
4~8MHz
2
0
0
0
0
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OSCRANGE
1
0
0
1
1
0
0
1
0
1
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