doc/html/ref/hal-diagnostic-support.html

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  85 NAME="HAL-DIAGNOSTIC-SUPPORT">Diagnostic Support</H1
  86 ><P
  87 >The HAL provides support for low level diagnostic IO. This is
  88 particularly useful during early development as an aid to bringing up
  89 a new platform. Usually this diagnostic channel is a UART or some
  90 other serial IO device, but it may equally be a a memory
  91 buffer, a simulator supported output channel, a ROM emulator virtual
  92 UART, and LCD panel, a memory mapped video buffer or any other output
  93 device.</P
  94 ><P
  95 ><TT
  96 CLASS="FUNCTION"
  97 >HAL_DIAG_INIT()</TT
  98 > performs any initialization
  99 required on the device being used to generate diagnostic output. This
 100 may include, for a UART, setting baud rate, and stop, parity and
 101 character bits. For other devices it may include initializing a
 102 controller or establishing contact with a remote device.</P
 103 ><P
 104 ><TT
 105 CLASS="FUNCTION"
 106 >HAL_DIAG_WRITE_CHAR(c)</TT
 107 > writes
 108 the character supplied to the diagnostic output device.</P
 109 ><P
 110 ><TT
 111 CLASS="FUNCTION"
 112 >HAL_DIAG_READ_CHAR(c)</TT
 113 > reads a character from the
 114 diagnostic device into the supplied variable. This is not supported
 115 for all diagnostic devices.</P
 116 ><P
 117 >These macros are defined in the header file
 118 <TT
 119 CLASS="FILENAME"
 120 >cyg/hal/hal_diag.h</TT
 121 >. This file is usually supplied
 122 by the variant or platform HAL, depending on where the IO device being
 123 used is located. For example for on-chip UARTs it would be in the
 124 variant HAL, but for a board-level LCD panel it would be in the
 125 platform HAL.</P
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