ARM Prospector P1100, User Manual, Page: 109 / 154

Programmer’s Reference
ARM DUI 0122A Copyright © ARM Limited 2000. All rights reserved. 4-23
4.4.4 Accessing the keyboard controller
To pass messages between the keyboard controller and SA-1100, you must:
1. Set the correct SPI chip-select value on the SA-1100 GPIO pins.
2. Enable the SPI chip-select decoder which is controlled by a GPIO pin on the
system controller PLD.
3. Manipulate the SPI clock signal, as described below.
4.4.5 Keyboard controller host interface timing
A number of SA-1100 GPIO pins are used for data transfers and interface timing
between the SA-1100 and keyboard controller.
Keyboard controller host writes
Figure 4-3 shows the timing for host writes to the keyboard controller.
Figure 4-3 SPI master timing: host writes to the keyboard controller
Host writes to the keyboard controller are as follows:
• Host transfers to the keyboard controller start with the assertion of
PLD_SPI_nCS0. The keyboard controller responds by asserting KEY_nATN
and driving CPU_SPI_RXD HIGH.
• The host must wait a minimum of 0.1ms and a maximum of 5ms before
beginning to transfer the first byte.
Last Byte
PLD_SPI_CS0
KEY_nATN
CPU_SPI_TXD
CPU_SPI_RXD
CPU_SPI_SCLK
Ist Byte 2nd Byte