Capabilities
Details
SpectraVideo CompuMate bankswitched games.
Image credit: http://www.oldcomputers.net/pics/spectravideo-compumate-atari.jpg
This is more than just a cartridge mapper - it's also a "computer" add-on. There are two 8K EPROMs soldered on top of each other. There's two short wires with DB-9s on them which you plug into the two controller ports. It has a membrane keyboard with 42 keys, audio in and audio out, and 2K of RAM.
There are 4 4K banks selectable at $1000 - $1FFF, and 2K RAM at $1800 - $1FFF (R/W 'line' is available at SWCHA D5, so there's no separate read and write ports).
Bankswitching is done though the controller ports
SWCHA: D7 = Audio input from tape player
D6 = Audio out to tape player and 4017 CLK
1 -> increase key column (0 to 9)
D5 = 4017 RST, and RAM direction. (high = write, low = read)
1 -> reset key column to 0 (if D4 = 0)
0 -> enable RAM writing (if D4 = 1)
D4 = RAM enable: 1 = disable RAM, 0 = enable RAM
D3 = keyboard row 3 input (0 = key pressed)
D2 = keyboard row 1 input (0 = key pressed)
D1 = bank select high bit
D0 = bank select low bit
INPT0: D7 = FUNC key input (0 on startup / 1 = key pressed)
INPT1: D7 = always HIGH input (pulled high thru 20K resistor)
INPT2: D7 = always HIGH input (pulled high thru 20K resistor)
INPT3: D7 = SHIFT key input (0 on startup / 1 = key pressed)
INPT4: D7 = keyboard row 0 input (0 = key pressed)
INPT5: D7 = keyboard row 2 input (0 = key pressed)
The keyboard's composed of a 4017 "1 of 10" counter, driving the 10 columns of the keyboard. It has 4 rows. The 4 row outputs are buffered by inverters.
Bit 5 of portA controls the reset line on the 4017. Pulling it high will reset scanning to column 0. Pulling it low will allow the counter to be clocked.
Bit 6 of portA clocks the 4017. Each rising edge advances the column one count.
There's 10 columns labelled 0-9, and 4 rows, labelled 0-3.
Column
0 1 2 3 4 5 6 7 8 9
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+
| 7 | | 6 | | 8 | | 2 | | 3 | | 0 | | 9 | | 5 | | 1 | | 4 | 0
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+
| U | | Y | | I | | W | | E | | P | | O | | T | | Q | | R | 1
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ Row
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+
| J | | H | | K | | S | | D | |ent| | L | | G | | A | | F | 2
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+
| M | | N | | < | | X | | C | |spc| | > | | B | | Z | | V | 3
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+
Function and Shift are separate keys that are read by 2 of the paddle inputs. These two buttons pull the specific paddle input low when pressed. Because the inputs are inverted, a low indicates a pressed button, and a high is an unpressed one.
The audio input/output are designed to drive a tape player. The audio output is buffered through an inverter and 2 resistors and a capacitor to reduce the level to feed it into the tape player. The audio input is passed through a .1 uf capacitor and is pulled to 1/2 supply by two 20 K resistors, then it goes through a hex inverting Schmitt trigger to square it up. This then runs into bit 7 of portA.
Use
SpectraVideo CompuMate bankswitched games.
Related
see Bank Switching