--- a/simtool/writecmd.c	Wed Feb 17 01:17:00 2021 +0000
+++ b/simtool/writecmd.c	Wed Feb 17 05:07:54 2021 +0000
@@ -63,3 +63,19 @@
 	}
 	return update_rec_op(recno, 0x04, data, curfile_record_len);
 }
+
+cmd_update_rec_prev(argc, argv)
+	char **argv;
+{
+	u_char data[255];
+	int rc;
+
+	rc = read_hex_data_file(argv[1], data);
+	if (rc < 0)
+		return(rc);
+	if (rc != curfile_record_len) {
+		fprintf(stderr, "error: hex data length != EF record length\n");
+		return(-1);
+	}
+	return update_rec_op(0, 0x03, data, curfile_record_len);
+}