Atari CX85

Atari CX85 Numerical Keypad
Atari CX85 with its 17 keys, including ESCAPE, NO, DELETE and YES down the left side
Manufacturer	Atari, Inc.
Type	Numeric keypad
Release date	1983
Price	US$124.95
Interface	Atari controller port (port 2)
Compatible	Atari 8-bit computers
Model	CX85; keypad CA060143-01
Power	+5 V from controller port pin 7

The Atari CX85 Numerical Keypad is a 17-key numeric keypad for the Atari 8-bit computers. It plugs into a controller port, not the SIO bus, and needs a software handler to work. Atari announced it in January 1982 and shipped it in early 1983, on its own and in The Bookkeeper Kit. Atari's CX85 field service manual, FD100176 of November 1982, gives a test program, a fault-finding guide, an assembly drawing, the schematic and the parts list.

History and packaging

Atari announced the keypad at the Winter Consumer Electronics Show in January 1982. At the launch of the 1200XL in December 1982 it promised the keypad again for spring 1983, and it shipped in about February 1983 at US$124.95. It was sold separately and as part of the CX419 Bookkeeper Kit with The Bookkeeper accounting program. The separate package held the CX8139 Numerical Keypad Handler Master Program Diskette, a keyboard overlay, the user's guide C060488 and Technical Reference Notes C061037. The keypads were made in Hong Kong. The FSM parts list shows two makers of the keypad board, assembly CA060140-01 made in Hi-Tek and CA060140-02 made by Atari Wong, and two FCC labels, one for units made in Hong Kong and one for units made in the USA.

Hardware

Figure 2 of the CX85 field service manual: the key matrix, the MCM74C923N encoder (IC2), the 4049B buffer (IC1), the cable pinout and the truth table

The keypad has no power supply or electrolytic capacitors. It takes +5 V and ground from pins 7 and 8 of the controller port. IC2, an MCM74C923N keyboard encoder, scans the keys. Its five data outputs and its key-down output pass through IC1, a 4049B inverter, to pins 1 to 4 (the joystick direction lines), pin 5 (the B paddle input) and pin 6 (the trigger). Pin 9, the A paddle input, is not used.

CX85 components (FSM parts list)

Position	Part	Atari part number
C1	0.01 µF ceramic disc, 12 V (alternative 0.01 µF 25 V ceramic axial)	2B-007 (C014181-02)
C2	0.47 µF ceramic axial, 25 V	C014181-07
C3	0.1 µF ceramic disc, 12 V (alternative 0.1 µF ceramic axial)	2C-001 (C014181-03)
IC1	4049B
IC2	MCM74C923N

The schematic carries the code each key puts on cable pins 5 to 1, where 1 is at least 4.0 V at −0.7 mA and 0 is at most 0.4 V at 3.2 mA:

CX85 truth table (FSM figure 2)

Key	Pins 5 4 3 2 1	Key	Pins 5 4 3 2 1
0	1 1 1 0 0	9	1 0 1 1 1
1	1 1 0 0 1	.	1 1 1 0 1
2	1 1 0 1 0	−	1 1 1 1 1
3	1 1 0 1 1	+ENTER	1 1 1 1 0
4	1 0 0 0 1	F1 (ESCAPE)	0 1 1 0 0
5	1 0 0 1 0	F2 (NO)	1 0 1 0 0
6	1 0 0 1 1	F3 (DELETE)	1 0 0 0 0
7	1 0 1 0 1	F4 (YES)	1 1 0 0 0
8	1 0 1 1 0

Atari's own keypad driver uses the same codes. Flora P. Ng's interrupt handler of 8 March 1982 reads the keypad in port 2 during the deferred vertical blank, takes the B paddle bit from ALLPOT ($D208), and translates the codes through a table: $1C (binary 11100) for 0, $19 for 1, $0C for function 1 and so on, which agrees with the FSM table. The handler is the KEYPAD.OBJ and KEYPAD.SRC pair on the CX8139 diskette, a boot disk that loads the handler and then asks for the program diskette. Atari promoted it for use with VisiCalc.

Testing

The FSM test needs no special tools, only a computer (the manual names the Atari 400) and this BASIC program. The program disables the computer keyboard apart from BREAK and SYSTEM RESET, so save it first.

10 GRAPHICS 0:DIM FUNC$(10):PRINT:PRINT
20 POKE 755,0:IF PEEK(645)=1 THEN 20
30 POKE 77,0:STICK1=PEEK(633)
40 ALLPOT=PEEK(53768):IF ALLPOT=0 THEN 40
50 IF ALLPOT=255 AND STICK1=12 THEN STICK1=16
60 FOR X=0 TO STICK1:READ A:NEXT X:IF A>9 THEN 80
70 PRINT A;" ";:GOTO 90
80 RESTORE 200:FOR X=0 TO A-10:READ FUNC$:NEXT X:PRINT FUNC$;" ";
90 FOR T=0 TO 50:NEXT T:RESTORE:GOTO 20
100 DATA 10,4,5,6,11,7,8,9,12,1,2,3,0,13,14,15,16
200 DATA DELETE,NO,YES,.,+ ENTER,-,ESCAPE

1. Plug the keypad into controller port 2.
2. Run the program.
3. Press each key once and check that the screen shows the right response (1 for 1, - for -, NO for NO and so on). A key held down repeats.
4. If every key responds correctly, the keypad is good. Check that the owner is following the operator's manual and using port 2; if the complaint remains, suspect the handler diskette or the computer.
5. If keys respond wrongly, check that the program was typed correctly and that the plug is fully home in port 2, then use the fault table below.

Faults

Atari restricts repair to replacing the cable or the keypad board assembly.

CX85 troubleshooting guide (FSM pp. 2 and 3)

Symptom	Checks
No response from any key	Check the cable wiring to the board against the colour code in figure 1. Measure between pin 7 (violet, +5 V) and pin 8 (grey, ground); if there is no +5 V, replace the cable. Check for +5 V at pin 1 of IC1 and pin 20 of IC2. If it is missing, look for a cold solder joint or a cut track on the underside of the board; if neither, replace the keypad board.
No response from one or two keys	Pull off the keycaps and check that the spring contacts close when the key is pressed.
Wrong response from all keys	Check the cable against the colour code in figure 1. The board may have a faulty IC: replace the keypad assembly (CA060140). Check the test program.
Wrong response from one or two keys	Check the cable connections at the board. Look for a solder bridge on the underside of the board.
Display keeps responding after the key is released	Check that the key is not rubbing on the case. Look for a solder bridge or cold joint on the underside of the board. Check whether the key contact is stuck closed.
Intermittent operation	Check that all cable connections are tight. Check the key switches for loose contacts.

The cable's wires are colour-coded at the board connector. Figure 1 of the FSM shows the order, brown, red, orange, yellow, green, blue, violet, grey and white along the board edge, and the troubleshooting guide identifies violet as +5 V on pin 7 and grey as ground on pin 8.

Service parts

Atari HCD CX85 keypad, CA060143-01

Part number	Description
C060141	Bottom enclosure
88-1006	Rubber foot
C061195	FCC label (made in Hong Kong)
C060168	FCC label (made in USA)
72-F612	Screw, #6 × 3/4 pan head Phillips
CA060158-01, CA060158-02	Cable assembly (alternatives)
CA060140-01, CA060140-02	Numeric keypad assembly (Hi-Tek, Atari Wong)
C060142	Top enclosure
C060139	Label, CX85 keypad

Software

Programs must load a handler to read the keypad. The comp.sys.atari.8bit FAQ lists several dozen programs with CX85 support, among them Atari's The Bookkeeper, Reeve Software's Super ReeveKey and many games published on the German Zong magazine disks.

Documentation

The field service manual is hosted and described on the Atari CX85 Documentation page.

Related pages

• Atari CX40
• Atari 1090
• Atari 800XL