diff --git a/PDP11/pdp11_xq.c b/PDP11/pdp11_xq.c
index 85308522..12d3c5dc 100644
--- a/PDP11/pdp11_xq.c
+++ b/PDP11/pdp11_xq.c
@@ -518,19 +518,22 @@ const char* const xqt_xmit_regnames[] = {
   "IBAL", "IBAH", "ICR", "", "SRQR", "", "", "ARQR"
 };
 
-const char* const xq_csr_bits[] = {
-  "RE", "SR", "NI", "BD", "XL", "RL", "IE", "XI",
-  "IL", "EL", "SE", "RR", "OK", "CA", "PE", "RI"
+BITFIELD xq_csr_bits[] = {
+  BIT(RE), BIT(SR), BIT(NI), BIT(BD), BIT(XL), BIT(RL), BIT(IE), BIT(XI),
+  BIT(IL), BIT(EL), BIT(SE), BIT(RR), BIT(OK), BIT(CA), BIT(PE), BIT(RI),
+  ENDBITS
 };
 
-const char* const xq_var_bits[] = {
-  "ID", "RR", "V0", "V1", "V2", "V3", "V4", "V5",
-  "V6", "V7", "S1", "S2", "S3", "RS", "OS", "MS"
+BITFIELD xq_var_bits[] = {
+  BIT(ID), BIT(RR), BIT(V0), BIT(V1), BIT(V2), BIT(V3), BIT(V4), BIT(V5),
+  BIT(V6), BIT(V7), BIT(S1), BIT(S2), BIT(S3), BIT(RS), BIT(OS), BIT(MS),
+  ENDBITS
 };
 
-const char* const xq_srr_bits[] = {
-  "RS0", "RS1", "",    "",    "",    "",    "",    "",
-  "",    "TBL", "IME", "PAR", "NXM", "",    "CHN", "FES"
+BITFIELD xq_srr_bits[] = {
+  BIT(RS0), BIT(RS1), BITNC,    BITNC,    BITNC,    BITNC,    BITNC,    BITNC,
+  BITNC,    BIT(TBL), BIT(IME), BIT(PAR), BIT(NXM), BITNC, BIT(CHN), BIT(FES),
+  ENDBITS
 };
 
 /* internal debugging routines */
@@ -926,16 +929,16 @@ t_stat xq_rd(int32* data, int32 PA, int32 access)
       break;
     case 6:
       if (xq->var->mode != XQ_T_DELQA_PLUS) {
-        sim_debug_u16(DBG_VAR, xq->dev, xq_var_bits, xq->var->var, xq->var->var, 0);
-        sim_debug    (DBG_VAR, xq->dev, ", vec = 0%o\n", (xq->var->var & XQ_VEC_IV));
+        sim_debug_bits(DBG_VAR, xq->dev, xq_var_bits, xq->var->var, xq->var->var, 0);
+        sim_debug     (DBG_VAR, xq->dev, ", vec = 0%o\n", (xq->var->var & XQ_VEC_IV));
         *data = xq->var->var;
       } else {
-        sim_debug_u16(DBG_VAR, xq->dev, xq_srr_bits, xq->var->srr, xq->var->srr, 0);
+        sim_debug_bits(DBG_VAR, xq->dev, xq_srr_bits, xq->var->srr, xq->var->srr, 0);
         *data = xq->var->srr;
       }
       break;
     case 7:
-      sim_debug_u16(DBG_CSR, xq->dev, xq_csr_bits, xq->var->csr, xq->var->csr, 1);
+      sim_debug_bits(DBG_CSR, xq->dev, xq_csr_bits, xq->var->csr, xq->var->csr, 1);
       *data = xq->var->csr;
       break;
   }
@@ -1991,7 +1994,7 @@ t_stat xq_wr_var(CTLR* xq, int32 data)
   else
     xq->dib->vec = 0;
 
-  sim_debug_u16(DBG_VAR, xq->dev, xq_var_bits, save_var, xq->var->var, 1);
+  sim_debug_bits(DBG_VAR, xq->dev, xq_var_bits, save_var, xq->var->var, 1);
 
   return SCPE_OK;
 }
@@ -2839,7 +2842,7 @@ void xq_csr_set_clr (CTLR* xq, uint16 set_bits, uint16 clear_bits)
   /* set the bits in the csr */
   xq->var->csr = (xq->var->csr | set_bits) & ~clear_bits;
 
-  sim_debug_u16(DBG_CSR, xq->dev, xq_csr_bits, saved_csr, xq->var->csr, 1);
+  sim_debug_bits(DBG_CSR, xq->dev, xq_csr_bits, saved_csr, xq->var->csr, 1);
 
   /* check and correct the state of controller interrupt */
 
diff --git a/scp.c b/scp.c
index a40cccb8..a406deaf 100644
--- a/scp.c
+++ b/scp.c
@@ -5860,19 +5860,49 @@ if (!debug_unterm) {
 }
 
 /* Prints state of a register: bit translation + state (0,1,_,^)
-   indicating the state and transition of the bit. States:
+   indicating the state and transition of the bit and bitfields. States:
    0=steady(0->0), 1=steady(1->1), _=falling(1->0), ^=rising(0->1) */
 
-void sim_debug_u16(uint32 dbits, DEVICE* dptr, const char* const* bitdefs,
-    uint16 before, uint16 after, int terminate)
+void sim_debug_bits(uint32 dbits, DEVICE* dptr, BITFIELD* bitdefs,
+    uint32 before, uint32 after, int terminate)
 {
 if (sim_deb && (dptr->dctrl & dbits)) {
-    int32 i;
+    int32 i, fields, offset;
+    uint32 value, beforevalue, mask;
 
+    for (fields=offset=0; bitdefs[fields].name; ++fields) {
+        if (bitdefs[fields].offset == -1)               /* fixup uninitialized offsets */
+            bitdefs[fields].offset = offset;
+        offset += bitdefs[fields].width;
+        }
     sim_debug_prefix(dbits, dptr);                      /* print prefix if required */
-    for (i = 15; i >= 0; i--) {                         /* print xlation, transition */
-        int off = ((after >> i) & 1) + (((before ^ after) >> i) & 1) * 2;
-        fprintf(sim_deb, "%s%c ", bitdefs[i], debug_bstates[off]);
+    for (i = fields-1; i >= 0; i--) {                   /* print xlation, transition */
+        if (bitdefs[i].name[0] == '\0')
+            continue;
+        if ((bitdefs[i].width == 1) && (bitdefs[i].valuenames == NULL)) {
+            int off = ((after >> bitdefs[i].offset) & 1) + (((before ^ after) >> i) & 1) * 2;
+            fprintf(sim_deb, "%s%c ", bitdefs[i].name, debug_bstates[off]);
+            }
+        else {
+            char *delta = "";
+
+            mask = 0xFFFFFFFF >> (32-bitdefs[i].width);
+            value = ((after >> bitdefs[i].offset) & mask) + (((before ^ after) >> bitdefs[i].offset) & mask) * 2;
+            beforevalue = ((before >> bitdefs[i].offset) & mask);
+            if (value < beforevalue)
+                delta = "_";
+            if (value > beforevalue)
+                delta = "^";
+            if (bitdefs[i].valuenames)
+                fprintf(sim_deb, "%s=%s%s ", bitdefs[i].name, delta, bitdefs[i].valuenames[value]);
+            else
+                if (bitdefs[i].format) {
+                    fprintf(sim_deb, "%s=%s", bitdefs[i].name, delta, value);
+                    fprintf(sim_deb, bitdefs[i].format, value);
+                    }
+                else
+                    fprintf(sim_deb, "%s=%s0x%X ", bitdefs[i].name, delta, value);
+            }
         }
     if (terminate)
         fprintf(sim_deb, "\r\n");
diff --git a/scp.h b/scp.h
index 5dd0f6b1..b52d7633 100644
--- a/scp.h
+++ b/scp.h
@@ -125,8 +125,8 @@ char *match_ext (char *fnam, char *ext);
 const char *sim_error_text (t_stat stat);
 t_stat sim_string_to_stat (char *cptr, t_stat *cond);
 t_stat sim_cancel_step (void);
-void sim_debug_u16 (uint32 dbits, DEVICE* dptr, const char* const* bitdefs,
-    uint16 before, uint16 after, int terminate);
+void sim_debug_bits (uint32 dbits, DEVICE* dptr, BITFIELD* bitdefs,
+    uint32 before, uint32 after, int terminate);
 #if defined (__DECC) && defined (__VMS) && (defined (__VAX) || (__DECC_VER < 60590001))
 #define CANT_USE_MACRO_VA_ARGS 1
 #endif
diff --git a/sim_defs.h b/sim_defs.h
index 3d32500e..ccb4b78d 100644
--- a/sim_defs.h
+++ b/sim_defs.h
@@ -506,6 +506,14 @@ struct sim_debtab {
 #define DEBUG_PRI(d,m)  (sim_deb && (d.dctrl & (m)))
 #define DEBUG_PRJ(d,m)  (sim_deb && (d->dctrl & (m)))
 
+struct sim_bitfield {
+    char            *name;                              /* field name */
+    uint32          offset;                             /* starting bit */
+    uint32          width;                              /* width */
+    char            **valuenames;                       /* map of values to strings */
+    char            *format;                            /* value format string */
+    };
+
 /* File Reference */
 struct sim_fileref {
     char                name[CBUFSIZE];                 /* file name */
@@ -526,6 +534,12 @@ struct sim_fileref {
 #define BRDATA(nm,loc,rdx,wd,dep) #nm, (loc), (rdx), (wd), 0, (dep)
 #define URDATA(nm,loc,rdx,wd,off,dep,fl) \
     #nm, &(loc), (rdx), (wd), (off), (dep), ((fl) | REG_UNIT)
+#define BIT(nm)              {#nm, -1, 1}
+#define BITNC                {"",  -1, 1}
+#define BITF(nm,sz)          {#nm, -1, sz}
+#define BITNCF(sz)           {"",  -1, sz}
+#define BITFFMT(nm,sz,fmt)   {#nm, -1, sz, NULL, #fmt}
+#define BITFNAM(nm,sz,names) {#nm, -1, sz, names}
 #else
 #define ORDATA(nm,loc,wd) "nm", &(loc), 8, (wd), 0, 1
 #define DRDATA(nm,loc,wd) "nm", &(loc), 10, (wd), 0, 1
@@ -535,7 +549,14 @@ struct sim_fileref {
 #define BRDATA(nm,loc,rdx,wd,dep) "nm", (loc), (rdx), (wd), 0, (dep)
 #define URDATA(nm,loc,rdx,wd,off,dep,fl) \
     "nm", &(loc), (rdx), (wd), (off), (dep), ((fl) | REG_UNIT)
+#define BIT(nm)              {"nm", -1, 1}
+#define BITNC                {"",  -1, 1}
+#define BITF(nm,sz)          {"nm", -1, sz}
+#define BITNCF(sz)           {"",  -1, sz}
+#define BITFFMT(nm,sz,fmt)   {"nm", -1, sz, NULL, "fmt"}
+#define BITFNAM(nm,sz,names) {"nm", -1, sz, names}
 #endif
+#define ENDBITS {NULL}  /* end of bitfield list */
 
 /* Typedefs for principal structures */
 
@@ -550,6 +571,7 @@ typedef struct sim_schtab SCHTAB;
 typedef struct sim_brktab BRKTAB;
 typedef struct sim_debtab DEBTAB;
 typedef struct sim_fileref FILEREF;
+typedef struct sim_bitfield BITFIELD;
 
 /* Function prototypes */