Z86L7808PSC View Datasheet(PDF) - Zilog
Part Name
Description
MFG CO.
'Z86L7808PSC' PDF : 59 Pages View PDF
Z86L78
IR/Low-Voltage Microcontroller
Zilog
FUNCTIONAL DESCRIPTION (Continued)
Clock. The Z86L78 on-chip oscillator has a high-gain, par-
allel-resonant amplifier for connection to a crystal, LC, ce-
ramic resonator, or any suitable external clock source
(XTAL1 = Input, XTAL2 = Output). The crystal should be
AT cut, 1 MHz to 8 MHz maximum, with a series resistance
(RS) less than or equal to 100 Ohms. The Z86L7X on-chip
oscillator may be driven with a cost-effective RC network
or other suitable external clock source. For 32 kHz crystal
operation a mask option is selected which disables the in-
ternal XTAL1/2 feedback resistor. The external compo-
nents for using a 32 kHz crystal include a feedback (Rf)
and serial (Rd) resistor as shown in Figure 33.
The crystal should be connected across XTAL1 and
XTAL2 using the recommended capacitors (capacitance
greater than or equal to 22 pF) from each pin to ground.
The RC oscillator configuration is an external resistor con-
nected from XTAL1 to XTAL2, with a frequency-setting ca-
pacitor from XTAL1 to ground (Figure 32).
Power-On Reset (POR). A timer circuit clocked by a ded-
icated on-board RC oscillator is used for the Power-On Re-
set (POR) timer function. The POR time allows VCC and
the oscillator circuit to stabilize before instruction execu-
tion begins.
The POR timer circuit is a one-shot timer triggered by one
of three conditions:
1. Power Fail to Power OK status.
2. Stop-Mode Recovery (if D5 of SMR = 1).
3. WDT Time-Out.
The POR time is a nominal 5 ms. Bit 5 of the Stop-Mode
Register determines whether the POR timer is bypassed
after Stop-Mode Recovery (typical for external clock, RC,
LC oscillators).
XTAL1
XTAL1
XTAL1
C1
C1
C1
C1
Rf
L
R
XTAL2
XTAL2
C2
C2
XTAL2
C2
Rd
Ceramic Resonator or Crystal
C1, C2 = 47 pF TYP *
f = 8 MHz
* Preliminary value including pin parasitics
LC
C1, C2 = 22 pF
L = 130 µH *
f = 3 MHz *
RC
@ 3V VCC (TYP)
C1 = 33 pF *
R = 1K *
32 kHz XTAL
C1 = 20 pF, C = 33
pF
Rd = 56 - 470K
Rf =10 M
Figure 31. Oscillator Configuration
XTAL1
XTAL1
XTAL2
XTAL2
External Clock
2-40
DS97LVO0701
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