taskit Panel-Card, Technical Reference

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Hardware Description
9
• General Purpose Backup Registers
It is recommended to always use a backup power supply (normally a battery) in order to
speed up the boot-up time and to avoid reset problems.
4.7. Reset Controller (RSTC)
The embedded microcontroller has an integrated Reset Controller which samples the
backup and the core voltage. The presence of a backup voltage (VDDBU) when the card
is powered down speeds up the boot time of the microcontroller.
4.8. Serial Number
Every Panel-Card has a unique 48-bit hardware serial number chip which can be used by
application software. The chip is a Dallas
®
one-wire-chip. A Linux driver is provided.
4.9. Clock Generation
4.9.1. Processor Clocks
The embedded microcontroller generates its necessary clocks based on two crystal
oscillators: One slow clock (SLCK) oscillator running at 32.768 KHz and one main clock
oscillator running at 18.432 MHz. It has furthermore a internal slow clock oscillator, which
can be battery backed-up.
From the main clock oscillator, the microcontroller generates two further clocks by using
two PLLs. PLLA provides the processor clock (PCK) and the master clock (MCK). Typically
PLLB provides the 48 MHz USB Clock and is normally used only for this purpose. The
clocks of most peripherals derive from MCK. These include EBI, USART, SPI, TWI, SSC,
PIT and TC.
Some peripherals like the programmable clocks and the timer counters (TC) can also run
on SLCK. The real time timer (RTT) runs always on SLCK.
Clock Frequency Source
PCK (Processor Clock) 200 MHz PLLA
MCK (Master Clock) 100 MHz PLLA/2
USB Clock 48 MHz PLLB
Slow Clock 32.768 KHz Slow Clock Oscillator
Table 4.3. AT91SAM9261 Clocks
4.9.2. Programmable Clocks
The programmable clocks can be individually programmed to derive their input from
SLCK, PLLA, PLLB and Main Clock. Each PCK has a divider of 2, 4, 8, 16, 32 or 64.
The Panel-Card features four programmable clocks: PCK0, PCK1, PCK2 and PCK3.