VIPER
Detailed hardware description
To write to OUT[0:7], write to the following PXA255 processor GPIO lines to drive the
outputs.
VIPER Outputs
PXA255 GPIO
OUT0 GPIO20
OUT1 GPIO21
OUT2 GPIO22
OUT3 GPIO23
OUT4 GPIO24
OUT5 GPIO25
OUT6 GPIO26
OUT7 GPIO27
GPIO[20:27]
OUT[0:7]
OUT0B
PL9
Buffer
PXA255
The PXA255 GPIO lines must be configured using the registers built into the device to
ensure they function correctly. RedBoot configures GPIO20 – GPIO27 as outputs, and
sets OUT0 – 2 to logic ‘0’, and OUT3 – 7 as logic ‘1’. Eboot cannot set these up as
outputs as it only boots the Windows CE .NET image. Once Windows CE .NET is
booted you can simply write to a mapped address. For an example of how to do this
under Windows CE .NET please see the Windows CE .NET Technical Manual.
Please note:
•
•
IN0-7 cannot be configured as outputs as they are hardwired as input-only
by a buffer.
OUT0-7 cannot be configured as inputs as they are hardwired as
output-only by a buffer.
The GPIO lines are programmed using the GPCR0 and the GPSR0 to set the line to ‘0’
or ‘1’ respectively. The registers are 32-bit wide and bits 20-27 relate to GP20-27.
Register Address
GPCR0 0x40E00024
GPSR0 0x40E00018
The general-purpose inputs are 5V tolerant, and the outputs can sink and source up to
24mA @ 3.3V.
OUT0B is an inverted OUT0 signal, and is driven to 5V, which provides compatibility
with the VIPER-UPS.
© 2004 Arcom Issue H
40
