Intel STRONGARM SA-1100 - Manual (Page 67)

SA-1100 Developer’s Manual 8-1
Clocks
8
This section describes the Intel
®
StrongARM
®
SA-1100 Microprocessor (SA-1100) clocks. The
following diagram shows the distribution of clocks in the SA-1100. The 3.6864-MHz oscillator
feeds both PLLs. The primary PLL provides clocks for the core logic and a 7.36-MHz clock for
several of the serial controllers. The core, Dcaches, and read and write buffers use either the
full-speed core clock or the divided-down clock. The LCD controller, DMA, memory controller,
and GPIO use the core clock divided by 2 (RCLK). The 32.768-kHz oscillator feeds the real-time
clock (RTC) and the power manager logic. The secondary PLL provides the clock for the UDC, the
ICP, and the MCP. The oscillators and PLLs are completely integrated with the SA-1100 and
require no external devices other than the crystals for operation.
8.1 SA-1100 Crystal Oscillators
The SA-1100 clocks are derived from two crystals connected to onchip oscillators. The first clock
source is a 3.6864-MHz crystal that feeds the CPU PLL and the 48-MHz PLL. The CPU PLL
multiplies the oscillator output up to the core frequency. This frequency is then divided down to
generate baud rates for the serial ports. If the UARTs are not being used or do not need standard
baud rates, then the 3.6864 -Hz oscillator may be replaced with a 3.5795-MHz crystal to generate
frequencies as shown in
Table 8-1 .
The second oscillator is connected to a 32.768-kHz crystal. The output of this oscillator clocks the
power management controller and the real-time clock (RTC).
See Appendix B, “3.6864–MHz Oscillator Specifications” and Appendix C, “32.768–kHz
Oscillator Specifications” for detailed specifications of the crystal oscillators.
32.768-kHz
Oscillator 3.6864-MHz
Oscillator
Primary PLL
59 MHz – 200 MHz
Secondary PLL
48 MHz
ARM™
Icache
Dcache
Write
Buffer
Read
Buffer
I/O
Control
Memory
Controller
DMA
Controller
LCD
Controller
Divide
by 2
GPIO<27>
Peripherals
SDLC UART – 7.36 MHz
ICP – 7.36 or 48 MHz
MCP/SSP – 7.36 or 12 MHz
PPC – 7.36 MHz
UDC – 48 MHz
7.36 MHz
RTC
and
Power
Manager
SA-1 Core