--- a/simtool/writecmd.c	Mon Jan 25 01:54:43 2021 +0000
+++ b/simtool/writecmd.c	Mon Jan 25 02:16:16 2021 +0000
@@ -23,3 +23,26 @@
 	len = rc;
 	return update_bin_op(offset, data, len);
 }
+
+cmd_update_rec(argc, argv)
+	char **argv;
+{
+	unsigned recno;
+	u_char data[255];
+	int rc;
+
+	recno = strtoul(argv[1], 0, 0);
+	if (recno < 1 || recno > 255) {
+		fprintf(stderr,
+			"error: record number argument is out of range\n");
+		return(-1);
+	}
+	rc = read_hex_data_file(argv[2], 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(recno, 0x04, data, curfile_record_len);
+}