ST6383 View Datasheet(PDF) - STMicroelectronics
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Description
Manufacturer
ST6383 Datasheet PDF : 82 Pages
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ST6380, ST6381, ST6382, ST6383, ST6388, ST6389
3 CLOCKS, RESET, INTERRUPTS AND POWER SAVING MODES
3.1 ON-CHIP CLOCK OSCILLATOR
The internal oscillator circuit is designed to require
a minimum of external components. A crystal
quartz, a ceramic resonator, or an external signal
(provided to the OSCin pin) may be used to gener-
ate a system clock with various stability/cost trade-
offs. The typical clock frequency is 8MHz. Please
note that different frequencies will affect the oper-
ation of those peripherals (D/As, SPI) whose refer-
ence frequencies are derived from the system
clock.
The different clock generator connection schemes
are shown in Figure 10 and 11. One machine cycle
takes 13 oscillator pulses; 12 clock pulses are
needed to increment the PC while and additional
13th pulse is needed to stabilize the internal latch-
es during memory addressing. This means that
with a clock frequency of 8MHz the machine cycle
is 1.625µSec.
The crystal oscillator start-up time is a function of
many variables: crystal parameters (especially
RS), oscillator load capacitance (CL), IC parame-
ters, ambient temperature, and supply voltage.It
must be observed that the crystal or ceramic leads
and circuit connections must be as short as possi-
ble. Typical values for CL1 and CL2 are in the
range of 15pF to 22pF but these should be chosen
based on the crystal manufacturers specification.
Typical input capacitance for OSCin and OSCout
pins is 5pF.
The oscillator output frequency is internally divided
by 13 to produce the machine cycle and by 12 to
produce the Timers and the Watchdog clock. A
byte cycle is the smallest unit needed to execute
any operation (i.e., increment the program coun-
ter). An instruction may need two, four, or five byte
cycles to be executed (See Table 6).
Table 6. Instruction Timing with 8MHz Clock
Instruction Type
Branch if set/reset
Branch & Subroutine Branch
Bit Manipulation
Load Instruction
Arithmetic & Logic
Conditional Branch
Program Control
Cycles
5 Cycles
4 Cycles
4 Cycles
4 Cycles
4 Cycles
2 Cycles
2 Cycles
Execution
Time
8.125µs
6.50µs
6.50µs
6.50µs
6.50µs
3.25µs
3.25µs
Figure 10. Clock Generator Option 1
CRYSTAL/RESONATOR CLOCK
ST6xxx
OSCin
OSCout
CL1
CL2
VA0016B
Figure 11. Clock Generator Option 2
EXTERNAL CLOCK
ST6xxx
OSCin
OSCout
NC
VA0015C
Figure 12. OSCin, OSCout Diagram
OSCin, OSCout (QUARTZ PINS)
VDD
OSCin
1M
In
VDD
OSCout
VA00462
18/82
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