![Rabbit 3000 Скачать руководство пользователя страница 199](http://html2.mh-extra.com/html/rabbit/3000/3000_user-manual_3114034199.webp)
User’s Manual
191
14. R
ABBIT
3000 C
LOCKS
The Rabbit 3000 normally uses two clocks, the main clock and the 32.768 kHz clock. The
32.768 kHz clock is needed for the battery-backable clock, the watchdog timer, and the
cold-boot function. The main oscillator provides the run-time clock for the microproces-
sor. Figure 14-1 shows the oscillator circuits.
Figure 14-1. Rabbit 3000 Oscillator Circuits
NOTE: You may have to adjust resistors and capacitors for various frequencies and crys-
tal load capacitances. Main oscillator capacitor varies 15-33 pF (Pedram to check).
The 32.768 kHz oscillator is slow to start oscillating after power-on. For this reason, a
wait loop in the BIOS waits until this oscillator is oscillating regularly before continuing
the startup procedure. If the clock is battery-backed, there will be no startup delay since
the oscillator is already oscillating. The startup delay may be as much as 5 seconds. Crys-
tals with low series resistance (R < 35 k
Ω
) will start faster. The required oscillator circuit
is shown in Figure 14-1(a).
14.1 Low-Power Design
The power consumption is proportional to the clock frequency and to the square of the
operating voltage. Thus, operating at 3.3 V instead of 5 V will reduce the power consump-
tion by a factor of 10.9/25, or 43% of the power required at 5 V. The clock speed is
reduced proportionally to the voltage at the lower operating voltage. Thus the clock speed
at 3.3 V will be about 2/3 of the clock speed at 5 V. The operating current is reduced in
proportion to the operating voltage.
10 M
W
200 k
W
15 pF
15 pF
32.768 kHz
XTALB2
XTALB1
1 M
W
2 k
W
33 pF
33 pF
11.0592 MHz
(a) 32.768 kHz Oscillator
(b) Main Oscillator
To Rabbit 3000
CLK32K
Содержание 3000
Страница 1: ...Rabbit 3000 Microprocessor User s Manual 019 0108 020426 A...
Страница 8: ...Rabbit 3000 Microprocessor...
Страница 28: ...20 Rabbit 3000 Microprocessor...
Страница 73: ...User s Manual 65 6 RABBIT INTERNAL I O REGISTERS...
Страница 122: ...114 Rabbit 3000 Microprocessor...
Страница 138: ...130 Rabbit 3000 Microprocessor...
Страница 150: ...142 Rabbit 3000 Microprocessor...
Страница 188: ...180 Rabbit 3000 Microprocessor...
Страница 208: ...200 Rabbit 3000 Microprocessor...
Страница 228: ...220 Rabbit 3000 Microprocessor...
Страница 232: ...224 Rabbit 3000 Microprocessor...
Страница 238: ...230 Rabbit 3000 Microprocessor...
Страница 260: ...252 Rabbit 3000 Microprocessor...
Страница 266: ......