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bus_mem(9s)


NAME

  bus_mem - EISA/ISA: Describes EISA/ISA bus memory characteristics


SYNOPSIS

  _________________________
  Member Name	Data Type
  _________________________
  isram		int
  decode	int
  unit_size	int
  size		long
  start_addr	io_handle_t
  _________________________


MEMBERS

  isram
      Specifies whether the memory associated with the EISA/ISA option card
      is read-only memory (ROM) or random-access memory (RAM). The bus
      configuration code initializes this member during hardware
      autoconfiguration.  The EISA/ISA bus configuration code sets this
      member to one of the following values during hardware
      autoconfiguration:


      ____________________________________________________
      Value   Meaning
      ____________________________________________________
      0

	      The memory associated with the EISA option
	      card is ROM (read only).
      1

	      The memory associated with the EISA option
	      card is RAM (read/write).
      ____________________________________________________

  decode
      Specifies the number of address lines that an EISA option card decodes.
      The ISA bus support code does not use this member and thus it sets this
      member to the value zero (0). The EISA bus configuration code sets this
      member to one of the following values during hardware
      autoconfiguration:


      __________________________________________________
      Value   Meaning
      __________________________________________________
      0

	      The number of address lines that an EISA
	      option card descodes equals 20.
      1

	      The number of address lines that an EISA
	      option card decodes equals 24.


      2

	      The number of address lines that an EISA
	      option card decodes equals 32.
      __________________________________________________

  unit_size
      Specifies the number of bits in the I/O port associated with this
      EISA/ISA option card. The EISA/ISA bus configuration code sets this
      member to one of the following values during hardware
      autoconfiguration:


      _________________________________________________
      Value   Meaning
      _________________________________________________
      0

	      There is one byte (8 bits) in the I/O
	      port associated with this EISA/ISA option
	      card.
      1

	      There is one word (16 bits) in the I/O
	      port associated with this EISA/ISA option
	      card.
      2

	      There is one longword (32 bits) in the
	      I/O port associated with this EISA option
	      card.
      _________________________________________________

  size
      Specifies the size of the memory block for this EISA/ISA option card.
      The EISA/ISA bus configuration code sets the size of the memory block
      up to a maximum of 64 megabytes during hardware autoconfiguration.

  start_addr
      Specifies an I/O handle that indicates where the bus configuration code
      maps the memory block. The EISA/ISA bus configuration code sets the I/O
      handle during hardware autoconfiguration.


DESCRIPTION

  The bus_mem structure describes memory characteristics for an EISA option
  card. The bus configuration code initializes the members of the bus_mem
  structure during hardware autoconfiguration.	Device drivers call the
  get_config interface to obtain information stored in the members of the
  bus_mem data structure.


FILES

  <io/dec/eisa/eisa.h>


SEE ALSO

  Kernel Interfaces: get_config(9r)

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