keyspan_pda: Fix parse error with as31 version 2.3.1

keyspan_pda.S has an out-of-range decimal constant that looks
like it was really meant to be a binary constant.  Comparing
with the binary, it appears that as31 used to treat this as 0,
so change the source to use 0 and add a comment on this.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/keyspan_pda/keyspan_pda.S b/keyspan_pda/keyspan_pda.S
index 418fe69..602bcce 100644 (file)
--- a/keyspan_pda/keyspan_pda.S
+++ b/keyspan_pda/keyspan_pda.S
@@ -285,7 +285,12 @@ clear_rx_ring_loop:
        mov dptr,OUTC
        movx @dptr, a
        ;; setup the serial port. 9600 8N1.
-       mov a,#01010011         ; mode 1, enable rx, clear int
+       ;; Original source had:
+       ;;mov a,#01010011               ; mode 1, enable rx, clear int
+       ;; This was presumably meant to be a binary constant, but it's
+       ;; really decimal and out of 8-bit range.  as31 used to treat
+       ;; it as 0 and that seems to have worked, so carry on with 0.
+       mov a,#0
        mov SCON, a
        ;;  using timer2, in 16-bit baud-rate-generator mode
        ;;   (xtal 12MHz, internal fosc 24MHz)