Section 4 Cpu And Power Supply; 4700 Cpu Circuit Board Description; Processor - U28 - Teledyne 4700 Serivce Manual

4700 Refrigerated Sampler
Service Guide

Section 4 CPU and Power Supply

4.1 4700 CPU Circuit
Board Description
4.1.1 Processor – U28
This section contains circuit descriptions of the 4700's CPU and
power supply, as well as functional CPU board testing. Sche-
matics can be found at the end of the section.
Note
The CPU will undergo updates in summer 2008 making it
capable of receiving a signal from the power supply when AC
power is lost, and of switching the sampler to battery backup
power upon receiving this signal.
The following section describes the operation of the CPU compo-
nents.
The processor used is an Atmel AT91M55800A. This processor
uses an ARM 7 core. Various peripherals are built into the pro-
cessor. Features include:
• 10 bit analog to digital (a-to-d) converter
• 8 to 1 multiplexer which allows 8 external analog inputs
to be converted one at a time
• clock circuitry that allows the processor to run at
different speeds
• an internal real-time clock that can run on battery
• two crystals: a 16 MHz for the processor clocks, and a
32.768 KHz for the real time clock
• 2 UARTS for serial communication
• counter/timers that can count pulses from external
sources
• large number of parallel input/output ports
• internal chip select circuitry
• internal RAM
• operates on 3.3 volts
• has 24 address lines allowing it to address 16 M bytes
• 16-bit data bus
• 2 digital to analog converters (d-to-a)
4-1