st92f124 STMicroelectronics, st92f124 Datasheet - Page 137

• Manufacturer Part Number: st92f124
• Description: 8/16-bit Single Voltage Flash Mcu Family With Ram, E3 Tmemulated Eeprom, Can 2.0b And J1850 Blpd
• Manufacturer: STMicroelectronics

7.5 CRYSTAL OSCILLATOR
The on-chip components for the crystal oscillator
are an inverting circuit, polarised at the trip point.
The inverter is built around an n-channel transis-
tor, loaded with a current source and polarised
through a feedback resistor.
The current source is tailored to obtain a pseudo
sinusoidal signal at OSCOUT and OSCIN, reduc-
ing the electromagnetic emission. The inverter
stage is followed by a matching inverter, which is
followed in turn by a schmitt-triggered buffer.
In HALT mode, set by means of the HALT instruc-
tion, in STOP mode, and under control of the XT-
STOP bit, the oscillator is disabled. The current
sources are switched off, reducing the power dis-
sipation. The internal clock, CLOCK1, is forced to
a high level.
To exit the HALT condition and restart the oscilla-
tor, an external RESET pulse is required, having a
a minimum duration of T
Section 11 ELECTRICAL
It should be noted that, if the Watchdog function is
enabled, a HALT instruction will not disable the os-
cillator. This to avoid stopping the Watchdog if a
HALT code is executed in error. When this occurs,
the CPU will be reset when the Watchdog times
out or when an external reset is applied.
Figure 66. Crystal Oscillator
*Rd can be inserted to reduce the drive level,
when using low drive crystals
h
C
1
OSCIN
i
CRYSTAL CLOCK
l
d i
ST9
ST92F124/F150/F250 - RESET AND CLOCK CONTROL UNIT (RCCU)
STUP
CHARACTERISTICS).
OSCOUT
t l
(see
.
Rd *
Figure 70
C
2
and
Table 31. Maximum R
Legend:
C
OSCOUT (the value includes the external capacitance
tied to the pin plus the parasitic capacitance of the board
and of the device)
Note: The tables are relative to the fundamental quartz
crystal only (not ceramic resonator).
Figure 67. Internal Oscillator Schematic
Figure 68. External Clock
C
Freq.
5 MHz
4 MHz
3 MHz
1
OSCIN
1
, C
=C
R
CLOCK
INPUT
2
POL
: Maximum Total Capacitances on pins OSCIN and
2
I
LOAD
EXTERNAL CLOCK
OSCOUT
OSCIN
OSCOUT
33pF
S
ST9
120
220
80
V
values
DD
VR02116B
22pF
130
200
370
137/426
CLOCK1
9