The NCR5380 now supports 12-byte CDB's correctly (and no longer returns with the return value being undefined), and ignores excess writes to the CDB.

src/scsi/scsi_ncr5380.c

@@ -9,7 +9,7 @@
  *		Implementation of the NCR 5380 series of SCSI Host Adapters
  *		made by NCR. These controllers were designed for the ISA bus.
  *
- * Version:	@(#)scsi_ncr5380.c	1.0.18	2018/10/05
+ * Version:	@(#)scsi_ncr5380.c	1.0.19	2018/10/08
  *
  * Authors:	Sarah Walker, <http://pcem-emulator.co.uk/>
  *		TheCollector1995, <mariogplayer@gmail.com>
@@ -210,13 +210,15 @@ get_dev_id(uint8_t data)
 static int 
 get_cmd_len(int cbyte)
 {
-    int len;
+    int len = 12;
     int group;
 
     group = (cbyte >> 5) & 7;
 
-    if (group == 0) len = 6;
-    if (group == 1 || group == 2) len = 10;
+    if (group == 0)
+	len = 6;
+    if ((group == 1) || (group == 2))
+	len = 10;
 
     return(len);
 }
@@ -915,6 +917,7 @@ ncr_callback(void *priv)
 	ncr_t *ncr = &ncr_dev->ncr;
 	scsi_device_t *dev = &SCSIDevices[ncr->target_id];
 	int c = 0;
+	int64_t p;
 
 	ncr_log("DMA mode=%d\n", ncr->dma_mode);
 	
@@ -969,13 +972,12 @@ ncr_callback(void *priv)
 		}
 		else if (ncr->state == STATE_COMMAND)
 		{
-			int64_t p;
-			
 			/*Command phase, make sure the ICR ACK bit is set to keep on, 
 			because the device must be acknowledged by ICR*/
 			ncr_log("NCR ICR for Command=%02x\n", ncr->bus_host & BUS_ACK);
 			if (ncr->bus_host & BUS_ACK)
 			{
+				if (get_cmd_len(ncr->command[0]) < ncr->command_pos) {
 					/*Write command byte to the output data register*/
 					ncr->command[ncr->command_pos++] = BUS_GETDATA(ncr->bus_host);
 
@@ -1039,15 +1041,14 @@ ncr_callback(void *priv)
 							ncr->new_phase = dev->Phase;
 
 							if (ncr->new_phase == SCSI_PHASE_DATA_IN) 
-						{
 								scsi_device_command_phase1(ncr->target_id);
-						}
 
 							ncr->wait_data = 4;
 						}
 					}
 				}
 			}
+		}
 		else if (ncr->state == STATE_DATAIN)
 		{
 			dev = &SCSIDevices[ncr->target_id];