ARM Prospector P1100, User Manual, Page: 65 / 154

Hardware Description
ARM DUI 0122A Copyright © ARM Limited 2000. All rights reserved. 3-33
The keyboard controller has a typical power consumption of less than 1µA at 3V.
Packaged in a 80-pin thin quad flat pack (TQFP), it has a maximum SPI clock frequency
of 250KHz. The P1100 design supports the maximum clock rate.
During power-up the keyboard controller the SPI clock and transmit data inputs
CPU_SPI_SCLK
and
CPU_SPI_TXD
are pulled HIGH and the SPI portion of the buffer
(U23) is permanently enabled. This ensures the SPI clock and transmit data inputs to
the keyboard controller are held in their idle HIGH state until the SPI bus has been
configured in the SA-1100, and ensures that the keyboard controller powers up in SPI
mode.
For SPI bus timing requirements, see Keyboard controller host interface timing on
page 4-23.
3.9.1 Key scanning and debounce
The keyboard controller scans and debounces a keyboard matrix of up to 8 rows x16
columns. The default matrix for the device is the Fujitsu FKB7654 miniature keyboard
with which P1100 system units are equipped. The Fujitsu keyboard provides an IBM
PC-AT style key layout within a minimal package size.
The matrix layout registers within the keyboard controller are automatically updated
with data corresponding to this keyboard on power-up.
The controller provides rollover processing of any number of key presses and the
minimizes ghost keys occurring when three or more keys are pressed. When a key is
pressed, the keyboard controller asserts
KEY_nATTN
to signal an interrupt request to
the PLD interrupt controller.
For information about keyboard controller interrupts, see Keyboard controller
interrupts on page 4-25.
3.9.2 LED control
The keyboard controller features a 4-bit GPIO port which is used to control four LEDS.
Each bit has a high current sink capability (20mA peak, 15mA average). On system
units, these ports are also used to control the LEDs on the distribution board which