Intel manual Clocks, SA-1100 Crystal Oscillators, Rtc, Arm, Lcd Dma

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.

32.768-kHz		3.6864-MHz
Oscillator		Oscillator
			Primary PLL
			59 MHz – 200 MHz
	RTC
	and
	Power			Secondary PLL
	Manager
				48 MHz

	ARM™
	SA-1 Core
Divide
by 2	Icache
	Dcache
7.36 MHz	Write
	Buffer
	Read
	Buffer

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

LCD	DMA	Memory	I/O
Controller	Controller	Controller	Control

8.1SA-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.

SA-1100 Developer’s Manual 8-1