Control Pad (Mega Drive)
From Sega Retro
The Sega Mega Drive Control Pad (コントロールパッド) is the official controller of the Sega Mega Drive (or Sega Genesis in North America). Three button controllers are known officially as Control Pads in both North America and Europe, and SJ-3500s in Japan (following a system set up by the SG-1000). There are many "updates" and alternatives to this controller, the most notable being the Six Button Control Pad. This article covers only the basic three button variants.
Mega Drive control pads are the logical progression from Master System control pads, replacing and with and respectively, while adding an extra two face buttons, and to bring the total number of buttons to four. Also featured is a circular D-Pad, designed to allow for movements in eight directions. Unlike Nintendo's systems, the buttons (or "triggers" as they were initially called) are arranged in alphabetical order from left to right, a practise which would continue not only with future Sega consoles, but would inspire the controllers of the Neo Geo, 3DO and Xbox lines.
Mega Drive controllers are notable for being one of the first control pads to be ergonomically designed for the user's hands. Though improvements were made in the coming years, previous systems had cornered edges with their controllers, meaning they were often uncomfortable to hold after several hours of play. The Mega Drive controller is rounded, and has its buttons placed in easier to reach positions.
Control pads remained mostly the same across regions, but the colouring can determine the region and revision of the accessory.
The first controller for the Sega Mega Drive, released in 1988. The , and buttons are printed in red lettering and the button is blue. The text at the top of the controller reads "Computer Video Game Control Pad". Later revisions removed the red lettering from the action buttons.
Sega Genesis Control Pad (MK-1650)
Initial Sega Genesis three-button controllers had a white button, with red coloured text. The arrows surrounding the D-Pad are also coloured red, and the printed text in the middle reads "Sega Genesis". These controllers match the original Genesis, and were distributed with the console during its early years.
Sega Genesis Control Pad (v2) (MK-1650)
As the original Genesis was revised during the early 1990s, so were the controllers. The arrows were changed to white and the text was left black. The text "TRIGGER" was moved below the three buttons, and extra labels for , and were added on top. This controller was also packaged with the Genesis 2 console.
Early versions of this controller used the same internals as the original design, but later models have an improved D-Pad mechanism, employing a metal ball-bearing for the pad to rock on. This prevented the wear which plagued the original design, which used a plastic nub for the rocking motion and would eventually wear down with frequent use. A minor addition is a little plastic lump on the button, presumably to help users recognise where their right hand thumb was.
Sega Genesis Control Pad (v3) (MK-1650)
Though this controller appears to be identical to the above, it once again has an updated D-pad. This was the first iteration of Sega's two-piece D-pad mechanism, used in every official subsequent controller up to and including the Sega Saturn's. Rather than providing the rocking motion by a plastic nub or ball-bearing, there is a molded dome underneath the outside half of the D-pad which allows the D-pad to glide smoothly in a circle. This design was also plagued with wear like the first model, eventually resulting in all four directions being able to be pressed simultaneously.
Sega Genesis Control Pad (Canada) (Older)
During its early years, the Canadian Genesis had its own packaging, handled by Irwin Toy.
Sega Genesis Control Pad (Canada) (Newer)
Sega Mega Drive Control Pad
Almost identical to the second Sega Genesis three-button gamepad, the first European Mega Drive controller sports a white button, the text "SEGA" and "Mega Drive Control Pad", and red lettering on the action buttons and red-coloured arrows around the D-pad.
Sega Mega Drive Control Pad (revised)
Sega Mega Drive Control Pad II
This revised version of the original Mega Drive controller was released with the revised Sega Mega Drive II, with the main change being a red button to match the red power and reset buttons on the console. This would become the most common Mega Drive controller, as far more Model IIs were sold in Europe than Model Is.
Super Aladdin Boy Control Pad
The control pad that debuted along with Korea's Super Aladdin Boy is very similar to the first Japanese model. It contains a blue button, red button text and the text "COMPUTER VIDEO GAME CONTROL PAD" printed on top. This is all rounded off with a Samsung logo in the middle.
The chip inside the control pad is a 74HC157. This is a high-speed CMOS quad 2-line to 1-line multiplexer. Basically, how this works is there are two inputs ( A and B ) for every output ( Y ). There are four groups like this. There is one select signal for the whole chip. When the select signal is low, the output ( Y ) is the same as input A. When the select signal is high, the output Y is the same as input B. The pinout for the chip is as follows:
All the controls are done with switches. Up is a switch, Down is a switch, etc. Now, I will be referring to the output of these switches later on. The output is usually high when the switch isn't pressed. When the button is pushed, the output goes low. This is accomplished by connecting the output to +5V through a 10k resistor. The button is then attached between the output and ground. It looks like this:
+5V -----/\/\/------+--------- Output 10k | | / | Ground -----/ -------+ button (normally open)
The line numbers are determined as follows, looking straight at the plug on the front of the Genesis the numbers are:
1 2 3 4 5 6 7 8 9
Access to controller ports is from bytes $A10003 (controller 1) and $A10005 (controller 2). TH must be set for output and the other pins for input, so bytes $A10009 and $A1000B must be set to $40 to read the respective controller.
Bit 7 latches the value written to it. It takes approximately the equivalent of two nop instructions for other types of controllers (such as the six-button controller) to respond to a TH change.