.. label for cross-referencing
.. _250425:

######
250425
######

* PCB ASSY NO. 250425
* Schematic Number #251469
* Released in 1984
* 8-pin board (CN5-Video port has 8 pins)
* reduced oscillator circuit


=====================
Components' placement
=====================

.. rst-class:: components-placement

+----------------+----------------------------------------------------+--------------------------+---------------------+
| PCB identifier | IC number                                          | IC type                  | Memory location/bit |
+================+====================================================+==========================+=====================+
| U1             | :ref:`6526 <6526>`                                 | CIA 1                    | $DC00-$DCFF         |
+----------------+----------------------------------------------------+--------------------------+---------------------+
| U2             | :ref:`6526 <6526>`                                 | CIA 2                    | $DD00-$DDFF         |
+----------------+----------------------------------------------------+--------------------------+---------------------+
| U3             | :ref:`901226 <901226>`                             | BASIC ROM                | $A000-$BFFF         |
+----------------+----------------------------------------------------+--------------------------+---------------------+
| U4             | 2364                                               | KERNAL ROM               | $E000-$FFFF         |
+----------------+----------------------------------------------------+--------------------------+---------------------+
| U5             | 2332                                               | CHARACTER ROM            | $D000-$DFFF         |
+----------------+----------------------------------------------------+--------------------------+---------------------+
| U6             | :ref:`2114 <2114>`                                 | SRAM 1K x 4              | $D800-$DBFF         |
+----------------+----------------------------------------------------+--------------------------+---------------------+
| U7             | :ref:`6510 <6510>`                                 | CPU                      | N/A                 |
+----------------+----------------------------------------------------+--------------------------+---------------------+
| U8             | 7406                                               | Logic NOT (Hex Inverter) | N/A                 |
+----------------+----------------------------------------------------+--------------------------+---------------------+
| U9             | :ref:`4164 <4164>`                                 | DRAM 64K x 1             | D1                  |
+----------------+----------------------------------------------------+--------------------------+---------------------+
| U10            | :ref:`4164 <4164>`                                 | DRAM 64K x 1             | D3                  |
+----------------+----------------------------------------------------+--------------------------+---------------------+
| U11            | :ref:`4164 <4164>`                                 | DRAM 64K x 1             | D5                  |
+----------------+----------------------------------------------------+--------------------------+---------------------+
| U12            | :ref:`4164 <4164>`                                 | DRAM 64K x 1             | D7                  |
+----------------+----------------------------------------------------+--------------------------+---------------------+
| U13            | 74LS257                                            | Multiplexor              | N/A                 |
+----------------+----------------------------------------------------+--------------------------+---------------------+
| U14            | 74LS258                                            | Multiplexor              | N/A                 |
+----------------+----------------------------------------------------+--------------------------+---------------------+
| U15            | 74LS139                                            | Demultiplexor            | N/A                 |
+----------------+----------------------------------------------------+--------------------------+---------------------+
| U16            | 4066                                               | Quad Bilateral Switch    | N/A                 |
+----------------+----------------------------------------------------+--------------------------+---------------------+
| U17            | 82S100/906114-01                                   | PLA                      | N/A                 |
+----------------+----------------------------------------------------+--------------------------+---------------------+
| U18            | :ref:`6581 <6581>`                                 | SID                      | $D400-$D7FF         |
+----------------+----------------------------------------------------+--------------------------+---------------------+
| U19            | :ref:`6567 <6567>` (NTSC)/:ref:`6569 <6569>` (PAL) | VIC-II                   | $D000-$D3FF         |
+----------------+----------------------------------------------------+--------------------------+---------------------+
| U20            | LM556                                              | Dual Timer               | N/A                 |
+----------------+----------------------------------------------------+--------------------------+---------------------+
| U21            | :ref:`4164 <4164>`                                 | DRAM 64K x 1             | D0                  |
+----------------+----------------------------------------------------+--------------------------+---------------------+
| U22            | :ref:`4164 <4164>`                                 | DRAM 64K x 1             | D2                  |
+----------------+----------------------------------------------------+--------------------------+---------------------+
| U23            | :ref:`4164 <4164>`                                 | DRAM 64K x 1             | D4                  |
+----------------+----------------------------------------------------+--------------------------+---------------------+
| U24            | :ref:`4164 <4164>`                                 | DRAM 64K x 1             | D6                  |
+----------------+----------------------------------------------------+--------------------------+---------------------+
| U25            | 74LS257                                            | Multiplexor              | N/A                 |
+----------------+----------------------------------------------------+--------------------------+---------------------+
| U26            | 74LS373                                            | 8 bit 3-state Latch      | N/A                 |
+----------------+----------------------------------------------------+--------------------------+---------------------+
| U27            | 74LS08                                             | Logic AND                | N/A                 |
+----------------+----------------------------------------------------+--------------------------+---------------------+
| U28            | 4066                                               | Quad Bilateral Switch    | N/A                 |
+----------------+----------------------------------------------------+--------------------------+---------------------+
| U31            | :ref:`7701/8701 <8701>`                            | Oscillator               | N/A                 |
+----------------+----------------------------------------------------+--------------------------+---------------------+