Dreamcast Serial Transmission:
Using a CMOS/RS-232 Compatible Integrated Circuit Transciever

UNDER CONSTRUCTION!!





Introduction:
A wide range of companies produce integrated circuits for recieving and transmitting RS-232 type serial signals. These types of ICs are called 'Transcievers'. If we are intending to build an adapter for the Dreamcast, using one of these transcievers, we must make sure it is CMOS compatible. Any voltage over 5V coming into the Dreamcast's serial port could damage your Dreamcast. The Dreamcast sends 3.3V CMOS singals, and should recieve signals of the same type. Below is a list of some manufacturers of RS-232 transciever IC's:

-Maxim
-Sipex
-Analog Devices
-Texas Instruments
-Linear Technology
-On Semiconductor
-SGS Thomson Microelectronics
-ST Microelectronics

Maxim IC's are the most commonnly used and available, and are in the mid to high price range compared to other transceiver ICs.

Selecting a Proper Transciever Integrated Cicuit:
As you've probably deducted by now, in order to achieve Dreamcast <-> PC transmission, the singals on both ends must be converted. As stated earlier the Dreamcast serial port uses 3.3V CMOS signals and a PC's RS-232 serial port uses -15V to +15V signals. Hence the Dreamcast's singals will have to be "stepped up" and the PC's signals will have to be "stepped down". This is done using amplifiers specific to RS-232 and CMOS standards with the proper gains (Av=Gain=Vout/Vin, or Vout=Vin*Gain). The Dreamcast's signals will need an amplifier with a gain of approximately 5, and the PC's signals will need a "gain" of approximately 1/5 (.2).

Luckily there are a wide variety of transceiver IC's that perfrom the CMOS<->RS-232 signal conversion, most of which should be compatible with the Dreamcast. Contrary to some "unofficial Dreamcast developer's" initial speculations. There are a few differences between the CMOS/RS-232 compatible transcievers:

Transceiver Options:
-3V to 5.5V or 4.5V-5.5V Supply Voltage
-Enable/Shuttoff Modes or Always On
-16, 18 or 20 Pins
-DIP or Various Surface Mount Technology (SMT) Packages
-Internal or External Charge Capacitors

For choosing the right chip for your circuit, decide which of the previously mentioned features you'll need/want.
Ex. If you're building the circuit with a "VS-Cable", you'll want a IC than will run off 3.3V
Below is a list of several compatible IC's*
 -MAX3222
-MA3222 (Texas Instruments)
-MAX3232
-SP232A
-+more
*Not all IC's have been tested, but theoretically should function exactly the same
**Not tested or verified by me personally


Continue onto the Next Page for further details on designing a Dreamcast Serial interface with one of the transciever integrated circuits just discussed.
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