AT91EB42 Atmel, AT91EB42 Datasheet - Page 17

• Manufacturer Part Number: AT91EB42
• Description: KIT EVAL FOR ARM AT91M42800A
• Manufacturer: Atmel
• Series: AT91SAM Smart ARMr
• Type: MCUr

Specifications of AT91EB42

• Contents: Evaluation Board, Cable, Power Jack, CD-ROM
• For Use With/related Products: AT91M42800A
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

4.6
4.7
AT91EB42 Evaluation Board User Guide
Push-buttons,
LEDs, Reset and
Serial Interfaces
Layout Drawing
The IRQ0, TIOA0, PB6 and PB21 switches are debounced and buffered.
A supervisory circuit has been included in the design to detect and consequently reset
the board when the 3.3V supply voltage drops below 3.0V. Note that this voltage can be
changed depending on the board production series. The supervisory circuit also pro-
vides a debounced reset signal. This device can also generate the reset signal in case
of watchdog timeout as the pin NWDOVF of the AT91M42800A is connected to its input
MR.
The assertion of this reset signal will light up the red RESET LED (D10). By pressing the
CLEAR RESET push-button (S1), the LED can be turned off.
Another supervisory circuit initializes separately the microcontroller-embedded
JTAG/ICE interface when the 3.3V supply voltage drops below 3.0V. Note that this volt-
age can be changed, depending on the board production series. These separated reset
lines allow the user to reset the board without resetting the JTAG/ICE interface while
debugging.
The schematic (see Figure 6-5 on page 6-6 in Section 6, “Appendix B – Schematics”)
also shows eight general-purpose LEDs connected to Port B PIO pins (PB8 to PB15).
Two 9-way D-type connectors (P3/4) are provided for serial port connection.
Serial Port A (P3) is used primarily for host PC communication and is a DB9 female con-
nector. TXD and RXD are swapped so that a straight-through cable can be used. CTS
and RTS are connected together, as are DCD, DSR and DTR.
Serial Port B (P4) is a DB9 male connector with TXD and RXD obeying the standard
RS-232 pinout. Apart from TXD, RXD and ground, the other pins are not connected.
LEDs are connected to the TX and RX signals of both serial ports and show activity on
these serial links.
A MAX3223 device (U10) and associated bulk storage capacitors provide RS-232 level
conversion.
The layout diagram (see Figure 6-1 on page 6-2 in Section 6, “Appendix B – Schemat-
ics”) shows an approximate floor plan for the board. This has been designed to give the
lowest board area, while still providing access to all test points, jumpers and switches on
the board.
The board is provided with four mounting holes, one at each corner, into which feet are
attached. The board has two signal layers and two power planes.
1708C–ATARM–12-May-05
Circuit Description
4-3