Atmel AT91EB42 Section Circuit Description, Processor, Expansion, Connectors, Jtag Interface

Section 4

Circuit Description

4.1AT91M42800 Figure 6-1 on page 6-2shows the AT91M42800. The footprint is for a 144-pin TQFP

	Processor	package.
		Strap CB20 enables the user to choose between the standard ICE debug mode and the
		JTAG boundary scan mode of operation.
		The operating mode is defined by the state of the JTAGSEL input detected at reset.
		Jumper JP5 (see Figure 6-8 on page 6-9in Section 6, “Appendix B – Schematics”) can
		be removed by the user to allow measurement of the current demand by the whole
		microcontroller (VDDIO and VDDCORE). Jumper JP8 can be removed to measure the core
		microcontroller consumption (VDDCORE).
4.2	Expansion	The two expansion connectors, I/O expansion connector and EBI expansion connector,
	Connectors and	and the JTAG interface are described below.
	JTAG Interface	The I/O and EBI expansion connectors’ pinout and position are compatible with the
		other evaluation boards (except the I/O expansion connector pinout and position of the
		EB40) so that users can connect their prototype daughter boards to any of these evalu-
		ation boards.
4.2.1	I/O Expansion	The I/O expansion connector makes the general-purpose I/O (GPIO) lines, VCC3V3
	Connector	and Ground, available to the user. Configuration straps CB2, CB3, CB4, CB11, CB13,
		CB14, CB15, CB17, CB18 and CB19 are used to select between the I/O lines being
		used by the evaluation board or by the user via the I/O expansion connector. The con-
		nector is not fitted at the factory; however, the user can fit any 32 x 2 connector on a 0.1"
		(2.54 mm) pitch.
4.2.2	EBI Expansion	The schematic (Figure 6-4 on page 6-5in Section 6, “Appendix B – Schematics”) also
	Connector	shows the bus expansion connector which, like the I/O expansion connector, is not fitted
		at the factory. The user can fit any 32 x 2 connector on a 0.1" (2.54 mm) pitch to gain
		access to the data, address, chip select, read/write, oscillator output and wait request
		pins. VCC3V3 and ground are also available on this connector.

Configuration strap CB1, when open, allows the user to connect the EBI expansion con- nector to the MPI expansion connector of an AT91EB63 evaluation board without any conflicts.

4.2.3JTAG Interface An ARM®-standard 20-pin box header (P5) is provided to enable connection of an ICE interface to the JTAG inputs on the AT91. This allows code to be developed on the board without using system resources such as memory and serial ports.

AT91EB42 Evaluation Board User Guide 4-1