ARM Prospector P1100, User Manual, Page: 38 / 154

Hardware Description
3-6 Copyright © ARM Limited 2000. All rights reserved. ARM DUI 0122A
3.2 System clocks
The P1100 has three crystal oscillators. These supply clock references for the SA-1100
and the keyboard controller.
3.2.1 Processor clocks
Two crystal oscillators provide reference clock inputs for the SA-1100 as shown in
Figure 3-2.
Figure 3-2 SA-1100 clocks
The reference input from the 3.6864 MHz crystal is used to drive two on-chip
Phase-Locked Loops (PLLs), the primary and secondary PLLs.
The primary PLL supplies the core clock and a 7.36 MHz clock for some of the on-chip
serial ports. A divide-by-2 and buffered version of the core clock is used to drive
on-chip controllers and also appears on GPIO26 as
CPU_RCLK_OUT
.
The secondary PLL supplies a 48MHz clock for the GPIO-provided serial ports and pin
controllers. The reference clock from the 32.768 kHz crystal is used to drive an on-chip
Real-Time Clock (RTC) and power management controller. A buffered version of this
clock also appears on GPIO27. An RTC derived 1Hz signal appears on GPIO25.
The clocks available from GPIO pins are under software control (see GPIO pin
assignment on page 3-4).
ARM
SA-1
core
Write
buffer
Read
buffer
Dcache
Icache
DMA
controller
Memory
controller
Input/Output
controller
LCD
controller
32.768kHz
oscillator
3.6864MHz
oscillator
Primary PLL
59-200MHz
Secondary PLL
48MHz
RTC and
power manager
Divide by 2
Peripherals
GPIO[27] GPIO[25] GPIO[26]
7.36MHz