Open Access
Circuit Descriptions
3-4
ARM Development Board (ARM7TDMI Version)
Hardware Reference Guide
ARM DUI 0017C
3.2 ARM Development Board
The top-level schematic is illustrated in
A.1 Card Outline Drawing
on page A-2, and shows
the main blocks of the design. The blocks are interconnected by the ASB signals prefixed
B_, such as B_A[31:0], B_D[31:0] and B_WAIT. There are two ASB bus masters, the ARM
chip mounted on a header card and the test interface controller (TIC).
The ASB system modules (the system arbiter and decoder) can also be seen.
There is a block called ASB expansion which details the physical connectors. This allows the
ASB to be monitored by a logic analyser, or allows external circuitry to be attached
The oscillator block describes the system clock generation and distribution, and the power
supply block describes the power input and regulation.
There are a number of ASB slaves which are described in
3.2.3 ASB Slaves
on page 3-7.
3.2.1 Power Supply
This schematic is shown in
A.3 Power Supply
on page A-4.
Two green LEDs marked (5V) and (3V3) light up when power is connected to the board.
Note
Take care when connecting up power to this board as there is no protection for incorrectly
wired supplies. If the LEDs fail to light, switch off immediately and check the connections.
The board is designed to function at 5V so that high-speed programmable logic devices can
be used. The ARM processor is a 3.3V component and so needs to be protected from high
logic levels. This is accomplished through use of level-convertor ICs. A 3.3V supply is
generated on board from a 5V supply for use by the ARM processor and the synchronous
SRAM (a 3.3V part with 5V tolerant I/O).
Power to the board is supplied through a PC-style 12-way connector. This allows a PC power
supply to be connected directly, and this will provide all the requirements of the board. The
board consumes 2–5A at 5V depending upon the amount of DRAM fitted and the clock
frequency used. If preferred a bench power supply can be used instead.
Note
Some PC power supplies can trip out if very low current is taken, so you can insert a load
across the +12V supply has been made. If this is a requirement, connect a resistance across
the pads marked (JP2).
The connector (J1) contacts are rated at 2A, so if current consumption is low, it is only
necessary to connect to pin 2 (+5V) and pin 5 (GND). Pin 3 (+12V) need only be connected
if the PC card (PCMCIA) interface is to be used.
An LM317 voltage regulator (U1) is used to generate the 3.3V supply required by the ARM
processor. You can decouple this from the regulator by removing a wire link (JP1) if required.
hrg.book Page 4 Wednesday, July 22, 1998 9:18 AM