TT2500: Turtle Terminal 2500, from General Turtle Inc.

Custom TTL design by Marvin Minsky.  There are two displays: one
raster scan for bitmapped characters, and another random scan for
vector graphics.  There is also a keyboard, and a UART for talking
to a host computer.

The computer is normally booted off a ROM which reads and starts a
secondary loader from the UART.  The loader is responsible for reading
the payload, which comes in checksummed blocks.  The LOAD command
accepts files in same format.

tt2500/tests/test.ascii

@@ -0,0 +1 @@
+LOGO@@@@@@@@JAN@@A@A@@@AEJ\JtbJAN@@@EAA

tt2500/tests/tt2500_test.ini

@@ -0,0 +1,17 @@
+cd %~p0
+
+set tv disabled
+set crt disabled
+
+on error goto failed
+
+break 1235
+
+load test.ascii
+run 100
+
+:failed
+if (PC != 669) echof "\n*** TEST FAILED\n"; exit 1
+
+echof "\n*** TEST PASSED\n"
+exit 0