From b0f69eea9576cb989a28e25f20aa3454a65c055a Mon Sep 17 00:00:00 2001
From: Paul Koning <ni1d@arrl.net>
Date: Wed, 29 Mar 2023 20:07:26 -0400
Subject: [PATCH] PDP11: Support byte write access to DHCSR.

This fixes issue #201, using a fix proposed bu Bjoren Davis.
---
 PDP11/pdp11_dh.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/PDP11/pdp11_dh.c b/PDP11/pdp11_dh.c
index 030255cc..f22affdc 100644
--- a/PDP11/pdp11_dh.c
+++ b/PDP11/pdp11_dh.c
@@ -191,6 +191,17 @@ dh_wr(int32 data, int32 PA, int32 access)
   switch (PA & 017) {
   case 000:
     sim_debug (DBG_IO, &dh_dev, "WRITE DHSCR %06o\n", data);
+    if (access == WRITEB) {
+        /* Only writing one byte of "SCR" */
+        if ((PA & 1) == 0) {
+            /* Even byte offset */
+            data = (dh_scr & ~0377) | data;
+        }
+        else {
+            /* Odd byte offset */
+            data = (dh_scr & 0377) | (data << 8);
+        }
+    }
     dh_scr = data;
     if (data & MCLR)
       dh_reset (&dh_dev);