st92f120 STMicroelectronics, st92f120 Datasheet - Page 104

• Manufacturer Part Number: st92f120
• Description: 8/16-bit Flash Mcu Family With Ram, Eeprom And J1850 Blpd
• Manufacturer: STMicroelectronics

ST92F120 - RESET AND CLOCK CONTROL UNIT (RCCU)
7.5 OSCILLATOR CHARACTERISTICS
The on-chip oscillator circuit uses an inverting gate
circuit with tri-state output.
OSCOUT must not be used to drive external cir-
cuits.
When the oscillator is stopped, OSCOUT goes
high impedance.
In Halt mode, set by means of the HALT instruc-
tion, the parallel resistor, R, is disconnected and
the oscillator is disabled, forcing the internal clock,
CLOCK1, to a high level, and OSCOUT to a high
impedance state.
To exit the HALT condition and restart the oscilla-
tor, an external RESET pulse is required, having a
a minimum duration of 20 s, as illustrated in
ure
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 49. Crystal Oscillator
104/324
9
54.
*Recommended for oscillator stability
C
1
OSCIN
CRYSTAL CLOCK
ST9
1 M *
OSCOUT
C
2
VR02116A
Fig-
Table 23. 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 50. Internal Oscillator Schematic
Figure 51. External Clock
n
C
Freq.
5 MHz
4 MHz
3 MHz
1
1
, C
OSCOUT
=C
2
OSCIN
: Maximum Total Capacitances on pins OSCIN and
2
CLOCK
3.3 k
INPUT
S
Crystal Specification
EXTERNAL CLOCK
130 ohm
250 ohm
80 ohm
OSCOUT
OSCIN
33pF
ST9
BUFFER
CLOCK
HALT
INPUT
130 ohm
200 ohm
REF
22pF
VR02086A
VR02116B
-