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Mac Connectivity

 

 

OK, granted, not many people make their own cables any more; most Mac users will purchase the requisite cables to connect their various system components.

Sometimes though, managers of larger Mac-user facilities, as well as most techy-types, have cable fabrication capabilities and thus have the opportunity to save a few bucks per cable.

The most frequent requests I've had for information are to interface to multiscan VGA monitors and modems.

 


How to Connect Monitors to a Macintosh - Part 1

(If you have a large [17"-21"] VGA multiscan monitor, use this section, else go here.)

If you are fortunate to have a system (G3 or PowerMac) that supports multiple resolutions up to 1024x768 or even 1152x870, and have one of the new multi-sync monitors like a Viewsonic, Hitachi, or RasterOps, use the conner RasterOps, use the connector adapter shown below:

VGA connector

This adapter will allow you to use the resolutions button of the Control Strip to select any resolution from 640x480 to the max resolution, on-the-fly.


How to Connect Monitors to a Macintosh - Part 2

(Quadra, Centris, and later models)

The Mac Centris, Quadra, and later systems frame buffer determines what type of display is attached to the video connector by examining the state of 3 sense line pins. The following chart details how these three pins must be wired for each of the supported display types. For each supported display, the screen resolution (horiz. pixels X vertical pixels), bandwidth, and the vertical and horizontal scan rates are given. For the wiring of the rest of the pins, refer to Macintosh Video Pinout and your monitor's documentation.

The Mac Quadras, Centris series, and later models should support any display, whether from Apple or from another vendor, that meets one of the following specifications:

STANDARD SENSE CODES (1 or more of the sense pins grounded):
Display
Sense Pins
(see note 1)
Horiz & Vert
Band
Width
Vert
Refrsh
Horiz
Refrsh
 
10
7
4
Pixels
(MHz)
(Hz)
(KHz)
Apple 21" Color
0
0
0
1152 x 870
100
75
68.7
Apple Portrait
0
0
1
640 x 870
57.2832
75
68.9
12" AppleColor RGB
0
1
0
512 x 384
15.6672
60.15
24.48
Apple 2-page Mono.
0
1
1
1152 x 870
100
75
68.7
NTSC
1
0
0
underscan-512 x 384
12.2727
59.94
15.7
1
0
0
overscan-640 x 480
12.2727
59.94
15.7
(To produce a color NTSC signal, an RGB-to-NTSC converter is required.)

13" Apple Hi-Res Mono
1
1
0
640 x 480
30.24
66.7
35.0
13" AppleColor
Hi-Res RGB
1
1
0
640 x 480
30.24
66.7
35.0
Apple 16" Color Disp. (See Note 4.)
832 x 624
57.63
75
75
49.7
Portrait Color,
such as Radius
1
0
1
640 x 870
57.2832
75
68.9

Notes:

1) Sense pins 4, 7, and 10 are referred to as MON.ID1, MON.ID2, and MON.ID3 in the Macintosh pinout table or SENSE0, SENSE1, and SENSE2 in pinout tables for the video connectors. A sense pin value of 0 means that pin should be grounded to the C&VSYNC.GND signal (pin 11); a value of 1 means do not connect the pin. (See Macintosh Video Pinout )

2) Extended sense codes will be examined if the following sense code is detected: 1 1 1 (no sense pins grounded).

3) The terms 'underscan' and 'overscan' are used to describe the active video resolution for NTSC and PAL modes. Underscansolution for NTSC and PAL modes. Underscan means that the active video area appears in a rectangle centered on the screen with a black surrounding area. This ensures that the entire active video area always is displayed on all monitors. Overscan utilizes the entire possible video area for NTSC or PAL. However, most monitors or televisions will cause some of this video to be lost beyond the edges of the display, so the entire image will not be seen.

4) The Apple 16" Color Display should have pins 4 and 10 tied together and pin 7 should be unconnected. If used with a Macintosh Display Card, the Apple 16" Color Display also requires the Macintosh Display Card 4*8, 8*24, or 8*24 GC with revised ROMs.

 

EXTENDED SENSE CODES (enabled by not grounding any sense pins)

NOTE for extended sense codes: Sense pin pair value of 0 means those pins should be tied together (as opposed to grounding 10, 7, or 4 to pin 11); value of 1 means leave open. DON'T wire any of these pins to ground.

Display
Sense Pins
Horiz & Vert
Bandwidth
Refresh
Scan
 
4-10
10-7
7-4
Pixels
(MHz)
(Hz)
MHz)
16" color, such as
E-Machines
0
1
1
832 x 624
57.2832
75
49,7
PAL:
PAL has two wiring options, using the extended sense pin configuration.
To produce a color PAL signal, an RGB-to-PAL converter is required.
PAL option 1
0
0
0
underscan- 640 x 480
14.75
50
15.625
overscan- 768 x 576
14.75
50
15.625
PAL option 2
1
1*
0
underscan-640 x 480
14.75
50
15.625
overscan- 768 x 576
14.75
50
15.625
(*Note: This PAL option also requires a diode
between pins 10 and 7, with the cathode on 10)
VGA
1
0
1
640 x 480
25.175
59.95
31.47
Super VGA
1
0
1
800 x 600
36
56
35.16
(To enable Super VGA after configuring the sense pins and connecting the monitor for VGA, open the Monitors control panel and select Options. Choose Super VGA from the list and restart your system.)
19" color
1
1
0
1024 x 768
80
75
60.24
No external monitor
(video halted)
1
1
1

 

Macintosh Video Pinout:

Pin Signal Description
1 RED GND red video ground
2 RED VID red video
3 CYSNC composite sync
4 MON ID 1 monitor ID, bit 1 (also known as SENSE0)
5 GRN VID green video
6 GRN GND green video ground
7 MON ID 2 monitor ID, bit 2 (also known as SENSE1)
8 nc no connection
9 BLU VID blue video
10 MON ID 3 monitor ID, bit 3 (also known as SENSE2)
11 C&VSYNC GND CSYNC and VSYNC ground
12 VSYNC vertical sync
13 BLU GND blue video ground
14 HSYNC GND horizontal sync ground
15 HSYNC horizontal sync
Shell Chassis CHASSIS GND chassis ground

 

IF YOUR MONITOR IS A VGA TYPE, YOU CAN SIMPLY TRY THE FOLLOWING CABLE PINOUT:

A cable wired as follows may allow many different brands of VGA monitors to work on a Macintosh. Test the monitor on a Macintosh prior to purchase to see if it meets your expectations.

Basic VGA Adapter:

Macintosh Video
DB-15
Signal
VGA
Connector
Pin
2
red video
1
1
red gnd
6
9
Blue video
3
13
Blue gnd
8
5
Green video
2
6
Green gnd
7
15
HSync
13
12
VSync
14
7,10
Connect 7 and 10 together
so sense ID will equal VGA

 

There are a few issues to keep in mind with VGA monitors:

* VGA monitors will vary depending on the vendor. Check with the vendor about Macintosh compatibility before buying, or better yet, actually try the monitor to see if it works and if the quality is acceptable.

* Vendors have different image quality specifications. There may be significant differences between Apple monitors and the wide range of VGA monitors. Do a side-by-side comparison of the monitors you are considering before buying.

* Many third party cable vendors have off-the-shelf cables that should work.

 

MACINTOSH TO NTSC VIDEO CABLE EXAMPLE:

Most NTSC devices use an RCA-type phono connector and the following diagram uses that as a reference point. A cable wired as follows may allow many different brands of NTSC monity different brands of NTSC monitors to work on a Macintosh Centris or Quadra. We advise you to test the monitor on one of these machines prior to purchase to see if it meets your expectations. Adjust the phono connector side to whatever type of connector is used (RCA, BNC, etc.). "Tip" is the pin in the center of the connector (the signal); the sleeve is the flange around the outer edges of the connector (the chassis ground).

 

Card
DB-15 Connector
RCA-Type Phono Connector
4 MON_ID1 (SENSE0) ------------|
------------| connect these three together
------------|
7 MON_ID2 (SENSE1)
11 C&VSYNC_GND
5 GRN_VID -----> Tip (signal)
Shell CHASSIS_GND -----() Sleeve (ground)

 

By grounding pin 4 and pin 7

By grounding pin 4 and pin 7 to pin 11, the Macintosh CPUs are told that an interlaced (NTSC) monitor is attached. The actual black and white video signal is on pin 5 and connects to the center (Tip) of the phono-plug. The shell of the card connector connects to the sleeve of the phono plug.

To acquire a color NTSC signal from a Quadra (or any Apple Macintosh display card), an RGB-to-NTSC converter is required, such as those available from RasterOps, Truevision, and Computer Friends.

 


Mac Modem Cable

The Mac requires seven (7) wires for hardware handshaking. See Hardware Handshaking Cable, below. It specifies pin-to-pin wiring between a Mac 8-pin DIN and a standard male DB-25 communications plug that most modems require.

 

Hardware Handshaking Cable

Mac Function
Mac DIN-8
Pin
RS-232 Function
DB-25
Pin
RxD (receive)
5
Receive Data
3
TxD (transmit)
3
Transmit Data
2
Ground
4,8
Ground
7
HSKi
2
CTS
5
HSKo
1
RTS and DTR
4,20
GPi
7
CD
8

 

Male DB-25 connectors are usually numbered, while Mac 8-pin DINs are frequently not. So here is a diagram of the male Mac 8-pin DIN connector, looking into the pins at the end that plugs into the Mac.

 

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