cop8ame9 National Semiconductor Corporation, cop8ame9 Datasheet - Page 21

• Manufacturer Part Number: cop8ame9
• Description: 8-bit Cmos Flash Microcontroller With 8k Memory, Dual Op Amps, Virtual Eeprom, Temperature Sensor, 10-bit A/d And Brownout Reset
• Manufacturer: National Semiconductor Corporation

10.0 Functional Description
10.8 OSCILLATOR CIRCUITS
The device has two crystal oscillators to facilitate low power
operation while maintaining throughput when required. Fur-
ther 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.
10.8.1 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
FIGURE 10. Reset Circuit Using Power-On Reset
20006314
FIGURE 9. Brownout Reset Operation
(Continued)
21
count. The value of the resistor is in the range of 0.5M to 2M
(typically 1.0M). Table 2 shows the component values re-
quired for various standard crystal values. Resistor R2 is
on-chip, for the high speed oscillator, and is shown for
reference. Figure 11 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.
*Applies to connection to low speed oscillator on port pins L0 and L1 only.
**See Note below.
R1 (kΩ)
5.6
0
0
0
0
TABLE 2. Crystal Oscillator Configuration,
R2 (MΩ)
On Chip
On Chip
On Chip
On Chip
20
T
A
= 25˚C, V
C1 (pF)
18–36
100
18
18
**
CC
= 5V
100–156
C2 (pF)
18–36
18
18
**
20006313
CKI Freq.
www.national.com
32.768
(MHz)
0.455
kHz*
10
5
1