TABLE 3. Startup Times
10.0 Functional Description
(Continued)
CKI Frequency
Startup Time
1–10 ms
10 MHz
3.33 MHz
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.
3–10 ms
1 MHz
3–20 ms
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:
455 kHz
10–30 ms
2–5 sec
32 kHz (low speed oscillator)
10.8.2 Clock Doubler
Manufacturer’s specified load cap = (C1 * C2) / (C1 + C2) +
Cparasitic
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.
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.
Low Speed Oscillator
High Speed Oscillator
20006316
20006315
FIGURE 11. Crystal Oscillator
10.9 CONTROL REGISTERS
10.9.2 PSW Register (Address X'00EF)
HC
C
T1PNDA
T1ENA
EXPND
BUSY
EXEN
GIE
10.9.1 CNTRL Register (Address X'00EE)
Bit 7
Bit 0
T1C3
Bit 7
T1C2
T1C1
T1C0
MSEL
IEDG
SL1
SL0
Bit 0
The PSW register contains the following select bits:
HC
C
Half Carry Flag
Carry Flag
The Timer1 (T1) and MICROWIRE/PLUS control register
contains the following bits:
T1PNDA Timer T1 Interrupt Pending Flag (Autoreload RA
in mode 1, T1 Underflow in Mode 2, T1A capture
edge in mode 3)
T1C3
T1C2
T1C1
T1C0
Timer T1 mode control bit
Timer T1 mode control bit
Timer T1 mode control bit
T1ENA Timer T1 Interrupt Enable for Timer Underflow
or T1A Input capture edge
Timer T1 Start/Stop control in timer
modes 1 and 2. T1 Underflow Interrupt
Pending Flag in timer mode 3
EXPND External interrupt pending
BUSY
EXEN
GIE
MICROWIRE/PLUS busy shifting flag
Enable external interrupt
MSEL
IEDG
Selects G5 and G4 as MICROWIRE/PLUS
signals SK and SO respectively
Global interrupt enable (enables interrupts)
External interrupt edge polarity select
(0 = Rising edge, 1 = Falling edge)
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
SL1 & SL0 Select the MICROWIRE/PLUS clock divide
by (00 = 2, 01 = 4, 1x = 8)
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