GPIO(3)                     (SA1100)                      GPIO(3)

     NAME
          gpio - access to GPIO registers

     SYNOPSIS
          bind -a #G /dev

          /dev/gpioclear
          /dev/gpioctl
          /dev/gpioedge
          /dev/gpioset
          /dev/gpiostatus

     DESCRIPTION
          The GPIO interface serves a one-level directory with five
          files that give access to the GPIO registers in the SA1100.
          See the SA1100 handbook for details of the function of the
          various registers.

          The control file gpioctl accepts commands to set individual
          bits in the edge detect registers.  Each control message has
          three space-separated fields:

               reg pin value

          where reg is a single character denoting a register, pin a
          bit within it, and val the value (0 or 1) for that bit.
          Valid choices for reg are: d (GPDR), r (GRER), f (GFER), and
          a (GAFR).  For example, the control message

               d 10 1

          sets bit 10 (following the handbook's bit-numbering conven-
          tions) in the GPIO pin direction register GPDR.

          The read-only file gpiostatus shows the names and values (in
          hexadecimal) of all GPIO registers.

          The remaining data files allow bits to be read by Sys->read
          requests and set by Sys->write requests.  When read, each
          file returns the value of a given register as a single 8
          digit hexadecimal number: gpioset and gpioclear both give
          the value of the level register, GPLR; and gpioedge gives
          the value of the edge dectect register, GEDR.  Each write
          request should present a single number in textual form,
          which is assumed to be hexadecimal by default.  The value is
          written to a GPIO register: gpioset corresponds to GPSR,
          gpioclear corresponds to GPCR, and gpioedge corresponds to
          GEDR.

     SOURCE

     GPIO(3)                     (SA1100)                      GPIO(3)

          /os/sa1100/devgpio.c