COP8AME9_14 Datasheet, PDF (22/102 Pages) Texas Instruments – COP8AME9 8-Bit CMOS Flash Microcontroller with 8k Memory, Dual Op Amps, Virtual EEPROM, Temperature Sensor, 10-Bit A/D and Brownout Reset

COP8AME9, COP8ANE9
SNOS930F – MARCH 2001 – REVISED MARCH 2013
www.ti.com
OSCILLATOR CIRCUITS
The device has two crystal oscillators to facilitate low power operation while maintaining throughput when
required. Further information on the use of the two oscillators is found in Section 7.0 Power Saving Features.
The low speed oscillator utilizes the L0 and L1 port pins. References in the following text to CKI will also apply to
L0 and references to G7/CKO will also apply to L1.
Oscillator
CKI is the clock input while G7/CKO is the clock generator output to the crystal. An on-chip bias resistor
connected between CKI and CKO is provided to reduce system part count. The value of the resistor is in the
range of 0.5M to 2M (typically 1.0M). Table 4 shows the component values required for various standard crystal
values. Resistor R2 is on-chip, for the high speed oscillator, and is shown for reference. Figure 13 shows the
crystal oscillator connection diagram. A ceramic resonator of the required frequency may be used in place of a
crystal if the accuracy requirements are not quite as strict.
R1 (kΩ)
0
0
0
5.6
0
Table 4. Crystal Oscillator Configuration,
T_A = 25°C, V_CC = 5V
R2 (MΩ)
C1 (pF)
C2 (pF)
On Chip
On Chip
On Chip
On Chip
20
18
18
18–36
100
**
18
18
18–36
100–156
**
CKI Freq.
(MHz)
10
5
1
0.455
32.768 kHz⁽¹⁾
(1) Applies to connection to low speed oscillator on port pins L0 and L1 only.
** See NOTE below.
The crystal and other oscillator components should be placed in close proximity to the CKI and CKO pins to
minimize printed circuit trace length.
The values for the external capacitors should be chosen to obtain the manufacturer's specified load capacitance
for the crystal when combined with the parasitic capacitance of the trace, socket, and package (which can vary
from 0 to 8 pF). The guideline in choosing these capacitors is:
Manufacturer's specified load cap = (C₁ * C₂) / (C₁ + C₂) + C_parasitic
C₂ can be trimmed to obtain the desired frequency. C₂ should be less than or equal to C₁.
Note: The low power design of the low speed oscillator makes it extremely sensitive to board layout and load
capacitance. The user should place the crystal and load capacitors within 1cm. of the device and must ensure
that the above equation for load capacitance is strictly followed. If these conditions are not met, the application
may have problems with startup of the low speed oscillator.
Table 5. Startup Times
CKI Frequency
10 MHz
3.33 MHz
1 MHz
455 kHz
32 kHz (low speed oscillator)
Startup Time
1–10 ms
3–10 ms
3–20 ms
10–30 ms
2–5 sec
Clock Doubler
This device contains a frequency doubler that doubles the frequency of the oscillator selected to operate the
main microcontroller core. The details of how to select either the high speed oscillator or low speed oscillator are
described in, Power Saving Features. When the high speed oscillator connected to CKI operates at 10 MHz, the
internal clock frequency is 20 MHz, resulting in an instruction cycle time of 0.5 µs. When the 32 kHz oscillator
connected to L0 and L1 is selected, the internal clock frequency is 64 kHz, resulting in an instruction cycle of
152.6 µs. The output of the clock doubler is called MCLK and is referenced in many places within this document.
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