User's guide: mention lpc2000 checksum issue

Folk almost certainly want to have OpenOCD compute the checksum
when they modify the vector table.  However, that almost guarantees
that "verify_image" will fail.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>

1 files changed, 10 insertions, 4 deletions

diff --git a/doc/openocd.texi b/doc/openocd.texi
index a0fc0fb6..05b6f4e8 100644
--- a/doc/openocd.texi
+++ b/doc/openocd.texi
@@ -4185,13 +4185,19 @@ which must appear in the following order:
 
 @itemize
 @item @var{variant} ... required, may be
-@var{lpc2000_v1} (older LPC21xx and LPC22xx)
-@var{lpc2000_v2} (LPC213x, LPC214x, LPC210[123], LPC23xx and LPC24xx)
-or @var{lpc1700} (LPC175x and LPC176x)
+@option{lpc2000_v1} (older LPC21xx and LPC22xx)
+@option{lpc2000_v2} (LPC213x, LPC214x, LPC210[123], LPC23xx and LPC24xx)
+or @option{lpc1700} (LPC175x and LPC176x)
 @item @var{clock_kHz} ... the frequency, in kiloHertz,
 at which the core is running
-@item @var{calc_checksum} ... optional (but you probably want to provide this!),
+@item @option{calc_checksum} ... optional (but you probably want to provide this!),
 telling the driver to calculate a valid checksum for the exception vector table.
+@quotation Note
+If you don't provide @option{calc_checksum} when you're writing the vector
+table, the boot ROM will almost certainly ignore your flash image.
+However, if you do provide it,
+with most tool chains @command{verify_image} will fail.
+@end quotation
 @end itemize
 
 LPC flashes don't require the chip and bus width to be specified.