VIPER Technical Manual

VIPER Technical ManualDetailed hardware descriptionTo write to OUT[0:7], write to the following PXA255 processor GPIO lines to drive theoutputs.VIPER outputsPXA255 GPIOOUT0GPIO20OUT1OUT2GPIO21GPIO22PXA255GPIO[20:27]TransceiverOUT[0:7]OUT0BPL9OUT3GPIO23OUT4GPIO24OUT5GPIO25OUT6GPIO26OUT7GPIO27The PXA255 GPIO lines must be configured using the registers built into the device toensure they function correctly. RedBoot configures GPIO20 – GPIO27 as outputs, andsets OUT0 to logic ‘0’, and OUT1 – 7 as logic ‘1’. Eboot cannot set these up as outputsas it only boots the Windows CE image. Once Windows CE is booted you can simplywrite to a mapped address. For an example of how to do this under Windows CEplease see the Windows CE Technical Manual.Please note:• IN0-7 cannot be configured as outputs as they are hardwired as input-onlyby a buffer.• OUT0-7 cannot be configured as inputs as they are hardwired asoutput-only by a buffer.• OUT6-7 are not available if the VIPER is fitted with the TPM IC.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. To setone of the GP20-27 signals to a logic ‘1’ write a ‘1’ to the corresponding GPSR0 bit. Toset one of the GP20-27 signals to a logic ‘0’ write a ‘1’ to the corresponding GPCR0 bit.To monitor the current state of a GP20-27 signal line read from GPLR0. A read-modifywriteoperation to GPLR0 will not change the state of the GP20-27 signal lines.RegisterGPLR0GPSR0GPCR0Address0x40E000000x40E000180x40E00024© 2007 Arcom Issue D 58