COMe-bHL6 / Features and Interfaces
4.3
Serial Peripheral Interface (SPI)
The Serial Peripheral Interface Bus or SPI bus is a synchronous serial data link standard named by Motorola that operates
in full duplex mode. Devices communicate in master/slave mode where the master device initiates the data frame.
Multiple slave devices are allowed with individual slave select (chip select) lines. Sometimes SPI is called a “four wire”
serial bus, contrasting with three, two, and one wire serial buses.
The SPI interface can only be used with a SPI flash device to boot from external BIOS on the
baseboard.
4.4
SPI boot
The COMe-bHL6 supports boot from an external SPI Flash. It can be configured by pin A34 (BIOS_DIS#0) and pin B88
(BIOS_DIS1#) in following configuration:
BIOS_DIS0#
BIOS_DIS1#
Function
open
open
Boot on-module BIOS
GND
open
Boot baseboard LPC FWH
open
GND
Baseboard SPI = Boot Device 1, on-module SPI = Boot Device 2
GND
GND
Baseboard SPI = Boot Device 2, on-module SPI = Boot Device 1
By default only SPI Boot Device 1 is used in configuration 3 & 4. Both SPI Boot Devices are
used by splitting the BIOS with modified descriptor table in customized versions only
Using an external SPI flash
To programm an external SPI flash follow these steps:
» Connect a SPI flash with correct size (similar to BIOS ROM file size) to the module SPI interface
» Open pin A34 and B88 to boot from the module BIOS
» Boot the module to DOS with access to the BIOS image and Firmware Update Utility provided on EMD Customer
Section
» Connect pin B88 (BIOS_DIS1#) to ground to enable the external SPI flash
» Execute Flash.bat to flash the complete BIOS image to the external SPI flash
» reboot
Your module will now boot from the external SPI flash when BIOS_DIS1# is grounded.
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