ST7263BK1 STMicroelectronics, ST7263BK1 Datasheet - Page 35

• Manufacturer Part Number: ST7263BK1
• Description: LOW SPEED USB 8-BIT MCU FAMILY WITH UP TO 32K FLASH/ROM, DFU CAPABILITY, 8-BIT ADC, WDG, TIMER, SCI and I2C
• Manufacturer: STMicroelectronics

Specifications of ST7263BK1

• 4, 8, 16 Or 32 Kbytes Program Memory: high density Flash (HDFlash), FastROM or ROM with Read-Out and Write protection

ST7263Bxx
6.2
6.2.1
6.2.2
Clock system
General description
The MCU accepts either a crystal or ceramic resonator, or an external clock signal to drive
the internal oscillator. The internal clock (f
frequency (f
clock used). The internal clock is further divided by 2 by setting the SMS bit in the
miscellaneous register.
Using the OSC24/12 bit in the option byte, a 12 MHz or a 24 MHz external clock can be
used to provide an internal frequency of either 2, 4 or 8 MHz while maintaining a 6 MHz for
the USB (refer to
The internal clock signal (f
signal consists of a square wave with a duty cycle of 50%.
The internal oscillator is designed to operate with an AT-cut parallel resonant quartz or
ceramic resonator in the frequency range specified for f
recommended when using a crystal, and
crystal and associated components should be mounted as close as possible to the input
pins in order to minimize output distortion and start-up stabilization time.
Table 8.
1. R
External clock
An external clock may be applied to the OSCIN input with the OSCOUT pin not connected,
as shown on
input. The equivalent specification of the external clock source should be used instead of
t
Figure 16. External clock source connections
OXOV
SMAX
(see
C
R
C
OSCOUT
SMAX
is the equivalent serial resistor of the crystal (see crystal specification).
OSCIN
R
Table 62: Control timing
P
OSC
Recommended Values for 24 MHz crystal resonator
Figure
(1)
), which is divided by 3 (and by 2 or 4 for USB, depending on the external
Figure
16. The t
18).
Recommended capacitance and resistance
CPU
OXOV
) is also routed to the on-chip peripherals. The CPU clock
1-10 MΩ
Doc ID 7516 Rev 8
56pF
56pF
20 Ω
specifications do not apply when using an external clock
EXTERNAL
characteristics).
CLOCK
OSCIN
Table 8
CPU
) is derived from the external oscillator
OSCOUT
NC
lists the recommended capacitance. The
1-10 MΩ
osc
47pF
47pF
25 Ω
. The circuit shown in
Reset and clock management
1-10 MΩ
22pF
22pF
70 Ω
Figure 17
35/186
is