COP8AME9 Datasheet, PDF (22/83 Pages) National Semiconductor (TI) – 8-Bit CMOS Flash Microcontroller with 8k Memory, Dual Op Amps, Virtual EEROM, Temperature Sensor,10-Bit A/D and Brownout Reset

10.0 Functional Description
(Continued)
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 = (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 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.
High Speed Oscillator
TABLE 3. 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
10.8.2 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.
Low Speed Oscillator
20006315
FIGURE 11. Crystal Oscillator
20006316
10.9 CONTROL REGISTERS
10.9.1 CNTRL Register (Address X'00EE)
T1C3 T1C2 T1C1 T1C0 MSEL IEDG
SL1
Bit 7
SL0
Bit 0
The Timer1 (T1) and MICROWIRE/PLUS control register
contains the following bits:
T1C3
Timer T1 mode control bit
T1C2
Timer T1 mode control bit
T1C1
Timer T1 mode control bit
T1C0
Timer T1 Start/Stop control in timer
modes 1 and 2. T1 Underflow Interrupt
Pending Flag in timer mode 3
MSEL
Selects G5 and G4 as MICROWIRE/PLUS
signals SK and SO respectively
IEDG
External interrupt edge polarity select
(0 = Rising edge, 1 = Falling edge)
SL1 & SL0 Select the MICROWIRE/PLUS clock divide
by (00 = 2, 01 = 4, 1x = 8)
10.9.2 PSW Register (Address X'00EF)
HC
Bit 7
C T1PNDA T1ENA
EXPND
BUSY
EXEN
GIE
Bit 0
The PSW register contains the following select bits:
HC
Half Carry Flag
C
Carry Flag
T1PNDA Timer T1 Interrupt Pending Flag (Autoreload RA
in mode 1, T1 Underflow in Mode 2, T1A capture
edge in mode 3)
T1ENA Timer T1 Interrupt Enable for Timer Underflow
or T1A Input capture edge
EXPND External interrupt pending
BUSY MICROWIRE/PLUS busy shifting flag
EXEN Enable external interrupt
GIE
Global interrupt enable (enables interrupts)
The Half-Carry flag is also affected by all the instructions that
affect the Carry flag. The SC (Set Carry) and R/C (Reset
Carry) instructions will respectively set or clear both the carry
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