Motorola M68EZ328ADS Touch Panel Interface, Signal Assignment for Touch Panel Controller

Freescale Semiconductor, Inc.

Hardware Description and Board Operation

For full description of the LCD signals, please refer to the MC68EZ328 User’s Manual.

3.9.2 Touch Panel Interface

ARCHIVED BY FREESCALE SEMICONDUCTOR, INC. 2005

Inc.

INC. 2005

MC68EZ328

PB6

IRQ5

SPMCLK

SPMTXD

SPMRXD

Touch Panel

VCC

ADS7843

S1-5

CS

S1-4

PENIRQ

DCLK

DIN

DOUT

TOP

RIGHT LEFT

BOTTOM

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Figure 3-9. Touch Panel Controller Interface

The M68EZ328ADS board is equipped with Burr-Brown Touch Panel Controller ADS7843. Figure 3-9shows the interface of Touch Panel Controller. Totally one I/O signal, one inter- rupt capable I/O signal and one set of SPIM signals from MC68EZ328 are used to imple- ment the touch panel circuitry. All of these signals can be shared for other devices when touch panel interface controller is being disabled. The on-board touch panel controller can be disabled by turning both DIP switches S1-4, S1-5 off.

Table 3-6. Signal Assignment for Touch Panel Controller

Signals	Function
	This set of serial port interface signals performs data transfer with
SPMRXD, SPMTXD, SPMCLK	ADS7843. For detailed operation on the SPI port, please refer to the
	MC68EZ328 User’s Manual.
~IRQ5	This signal is a MC68EZ328 interrupt capable I/O pin.
PB6	This MC68EZ328 general I/O signal is used to select the ADS7843 on data
	transfer.

The ADS7843 is a 12-bit sampling analog-to-digital converter (ADC) with a synchronous serial interface and low on-resistance switches for touch screens. The ADS7843 communi- cates with MC68EZ328 through SPI (Serial Peripheral Interface). In this case, ADS7843 is a slave, and MC68EZ328 is a master. For the detailed operation of ADS7843, please refer to its datasheet. The datasheet is available at the following web site.

http://www.burr-brown.com

For more details on the operation of resistive touch panel, please refer to Appendix B .

MOTOROLAM68EZ328ADS v2.0 USER’S MANUAL3-24

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