--- a/simtool/writecmd.c	Sun Mar 07 04:06:39 2021 +0000
+++ b/simtool/writecmd.c	Sun Mar 07 04:11:28 2021 +0000
@@ -71,3 +71,32 @@
 	}
 	return update_rec_op(recno, mode, data, curfile_record_len);
 }
+
+cmd_update_rec_imm(argc, argv)
+	char **argv;
+{
+	unsigned recno, mode;
+	u_char data[255];
+	int rc;
+
+	if (!strcmp(argv[1], "prev")) {
+		recno = 0;
+		mode = 0x03;
+	} else {
+		recno = strtoul(argv[1], 0, 0);
+		if (recno < 1 || recno > 255) {
+			fprintf(stderr,
+			"error: record number argument is out of range\n");
+			return(-1);
+		}
+		mode = 0x04;
+	}
+	rc = decode_hex_data_from_string(argv[2], data, 1, 255);
+	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(recno, mode, data, curfile_record_len);
+}