cop8cde9 National Semiconductor Corporation, cop8cde9 Datasheet - Page 20

• Manufacturer Part Number: cop8cde9
• Description: 8-bit Cmos Flash Microcontroller With 8k Memory, Virtual Eeprom, 10-bit A/d And Brownout Reset
• Manufacturer: National Semiconductor Corporation

www.national.com
4.0 Functional Description
The crystal and other oscillator components should be
placed in close proximity to the CKI and CKO pins to mini-
mize 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 = (C
C
C
should be less than or equal to C
Note: The low power design of the low speed oscillator
makes it extremely sensitive to board layout and load ca-
pacitance. The user should place the crystal and load ca-
pacitors 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.
*
**
Applies to connection to low speed oscillator on port pins L0 and L1 only.
parasitic
2
32 kHz (low speed oscillator)
See Note below.
R1 (k )
can be trimmed to obtain the desired frequency. C
5.6
0
0
0
0
TABLE 3. Crystal Oscillator Configuration,
CKI Frequency
3.33 MHz
455 kHz
10 MHz
1 MHz
R2 (M )
On Chip
On Chip
On Chip
On Chip
20
TABLE 4. Startup Times
High Speed Oscillator
T
A
= 25˚C, V
C1 (pF)
18–36
100
18
18
**
CC
1
20022515
.
= 5V
100–156
C2 (pF)
18–36
Startup Time
1
18
18
**
10–30 ms
* C
1–10 ms
3–10 ms
3–20 ms
2–5 sec
2
) / (C
(Continued)
FIGURE 12. Crystal Oscillator
CKI Freq.
32.768
(MHz)
1
0.455
kHz
10
+ C
5
1
*
2
) +
2
20
4.8.2 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.
4.9 CONTROL REGISTERS
CNTRL Register (Address X'00EE)
The Timer1 (T1) and MICROWIRE/PLUS control register
contains the following bits:
PSW Register (Address X'00EF)
The PSW register contains the following select bits:
Bit 7
T1C3
Bit 7
T1C3
T1C2
T1C1
T1C0
MSEL
IEDG
SL1 & SL0 Select the MICROWIRE/PLUS clock divide
HC
C
T1PNDA Timer T1 Interrupt Pending Flag (Autoreload RA
HC
T1C2
C
Half Carry Flag
Carry Flag
T1PNDA
Timer T1 mode control bit
Timer T1 mode control bit
Timer T1 mode control bit
Timer
modes 1 and 2. T1 Underflow Interrupt
Pending Flag in timer mode 3
Selects G5 and G4 as MICROWIRE/PLUS
signals SK and SO respectively
External
(0 = Rising edge, 1 = Falling edge)
by (00 = 2, 01 = 4, 1x = 8)
T1C1
Low Speed Oscillator
T1ENA
T1C0
T1
interrupt
Start/Stop
MSEL
EXPND
20022516
edge
IEDG
BUSY
control
polarity
SL1
EXEN
in
select
SL0
timer
Bit 0
GIE
Bit 0