From ed0969ba740e12ea2f4b3ddb90de8e741d10a42e Mon Sep 17 00:00:00 2001
From: Lars Brinkhoff <lars@nocrew.org>
Date: Sat, 28 Mar 2020 21:36:40 +0100
Subject: [PATCH] KA10: Implement 340 special interrupt gronking.

---
 PDP10/kx10_dpy.c | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/PDP10/kx10_dpy.c b/PDP10/kx10_dpy.c
index a2111dc..2f7039f 100644
--- a/PDP10/kx10_dpy.c
+++ b/PDP10/kx10_dpy.c
@@ -30,6 +30,29 @@
  * for PDP-6 described in
  * http://www.bitsavers.org/pdf/dec/graphics/H-340_Type_340_Precision_Incremental_CRT_System_Nov64.pdf
  *
+ * The MIT file .INFO.;340 INFO says:
+ *    ;CONI BITS OF THE 340 ARE:
+ *            ;2.9-2.7        MODE
+ *            ;2.4            VECT CONT LP(????)
+ *            ;2.3            VERTICAL EDGE HIT
+ *            ;2.2            LIGHT PEN HIT
+ *            ;2.1            HORIZONTAL EDGE HIT
+ *            ;1.9            STOP
+ *            ;1.8            DONE (CAUSES DATA INTERUPT)
+ *            ;1.6-1.4        SPECIAL PIA
+ *            ;1.3-1.1        DATA PIA
+ *    ;340 CONO BITS ARE:
+ *            ;2.3            CLEAR NO INK MODE
+ *            ;2.2            SET NO INK MODE (IN NO INK MODE, NO INTENSIFICATION CAN \
+ *     OCCUR) 
+ *            ;2.1            CLEAR HALF WORD MODE
+ *            ;1.9            SET HALF WORD MODE
+ *            ;1.8            RESUME DISPLAY (TO CONTINUE AFTER A SPECIAL INTERUPT)
+ *            ;1.7            INTIALIZE
+ *            ;1.6-1.4        SPECIAL PIA
+ *            ;1.3-1.1        DATA PIA
+ * ITS uses the "resume display" bit, so it has been implemented here.
+ *
  * 340C was used in the PDP-10 VB10C display system
  * http://bitsavers.informatik.uni-stuttgart.de/pdf/dec/pdp10/periph/VB10C_Interactive_Graphics_Terminal_Jul70.pdf
  *      "The basic hardware system consists of a 340/C display connected
@@ -138,6 +161,7 @@ extern uint64 SW;        /* switch register */
 #define CONI_INT_HE     0001000         /* I- b26: HOR EDGE */
 #define CONI_INT_SI     0000400         /* I- b27: STOP INT */
 #define CONI_INT_DONE   0000200         /* I- b28: done with second half */
+#define CONO_RESUME     0000200         /* -O b28: resume after special int */
 #define CONO_INIT       0000100         /* -O b29: init display */
 #define CONX_SC         0000070         /* IO special channel */
 #define CONX_DC         0000007         /* IO data channel */
@@ -253,6 +277,13 @@ t_stat dpy_devio(uint32 dev, uint64 *data) {
         uptr->STAT_REG |= *data & CONO_MASK;
         if (*data & CONO_INIT)
             dpy_update_status( uptr, ty340_reset(&dpy_dev), 1);
+        if (*data & CONO_RESUME) {
+            /* This bit is not documented in "H-340 Type 340 Precision
+               Incremental CRT System".  It is in the MIT file .INFO.;
+               340 INFO, and ITS does depend on it. */
+            ty340_clear(CONI_INT_VE | CONI_INT_LP | CONI_INT_HE);
+            dpy_update_status( uptr, ty340_status(), 0);
+        }
         sim_debug(DEBUG_CONO, &dpy_dev, "DPY %03o CONO %06o PC=%06o %06o\n",
                   dev, (uint32)*data, PC, uptr->STAT_REG & ~STAT_VALID);
         if (!sim_is_active(uptr))