Aside from the amount of RAM, the 64 also has an RS-232 serial port which was not included on the 32.

PCI Express x1 card with one RS-232 port

In the book PC 97 Hardware Design Guide, Microsoft deprecated support for the RS-232 compatible serial port of the original IBM PC design.

An RS-232 serial port can communicate to some embedded systems such as routers as an alternative to network mode of monitoring.

In many computing contexts, " TTY " has become the name for any text terminal, such as an external console device, a user dialing in to the system on a modem on a serial port device, a printing or graphical computer terminal on a computer's serial port or the RS-232 port on a USB-to-RS-232 converter attached to a computer's USB port, or even a terminal emulator application in the window system using a pseudo terminal device.

New features included 128 kB RAM, three-channel audio via the AY-3-8912 chip, MIDI compatibility, an RS-232 serial port, an RGB monitor port, 32 kB of ROM including an improved BASIC editor, and an external keypad.

The ZX Interface 1 add-on module included 8 kB of ROM, an RS-232 serial port, a proprietary LAN interface ( called ZX Net ), and an interface for the connection of up to eight ZX Microdrives – somewhat unreliable but speedy tape-loop cartridge storage devices released in July 1983.

It is frequently used to implement the serial port for IBM PC compatible personal computers, where it is often connected to an RS-232 interface for modems, serial mice, printers, and similar peripherals.

The back had all of the same ports as the Tandy 1000, except that the light pen port was replaced with an RS-232 serial port.

The A600 features Amiga compatible connectors including two DB9M ports for joysticks, mice, and light pens, a standard 25-pin RS-232 serial port and a 25-pin Centronics parallel port.

While such interfaces as Ethernet, FireWire, and USB all send data as a serial stream, the term " serial port " usually identifies hardware more or less compliant to the RS-232 standard, intended to interface with a modem or with a similar communication device.

Inter-operation with RS-232 devices may be impossible as the serial port cannot withstand the voltage levels produced and may have other differences that " lock in " the user to products of a particular manufacturer.

RS-232 has been standard for so long that the circuits needed to control a serial port became very cheap and often exist on a single chip, sometimes also with circuitry for a parallel port.

The A3000 has a number of Amiga compatible connectors including two DE-9 ports for joysticks, mice, and light pens, a standard 25-pin RS-232 serial port and a 25-pin Centronics parallel port.

) 1 × TTL serial port 1 × TTL / RS-232 serial port ( configurable )

Created by telecoms vendor Ericsson in 1994, it was originally conceived as a wireless alternative to RS-232 data cables.

RS-232 was first introduced in 1962 by the Radio Sector of the EIA.

Upper Picture: RS-232 signalling as seen when probed by an actual oscilloscope ( Tektronix MSO4104B ) for an uppercase ASCII " K " character ( 0x4b ) with 1 start bit ( always ), 8 data bits, 1 stop bit and no parity bits ( 8N1 ) Lower Picture: Same signal was inputted into an RS-232 to UART converter, the output is depicted.

Perhaps the final 7-bit restriction, primarily imposed due to the pervasive use of RS-232 protocol for serial ports between devices, notably computers and modems, was lifted in the mid-1990s when RS-232 was largely replaced with Ethernet and with USB.

Finally, there was the Synertek SYM-1 variant, which could be said to be a machine halfway between the KIM and the AIM ; it had the KIM's small display, and a simple membrane keyboard of 29 keys ( hex digits and control keys only ), but provided AIM-standard expansion interfaces and true RS-232 ( voltage level as well as current loop mode supported ).

This was not an issue for networking protocols, where lost packets are assumed and dealt with in the network stack, but represented a series problem for RS-232 data which had no internal form of flow control in the data stream.

As a result, performance on a Mac Plus was generally limited to about 9600 bit / s in RS-232 mode, and could only reliably maintain half of that if AppleTalk was active at the same time.

The C16's serial port ( Commodore's proprietary " serial IEEE-488 bus ", no relation to RS-232 and the like ) was the same as that of the VIC-20 and C64, which meant that printers and disk drives, at least, were interchangeable with the older machines.

A standard defining serial communication between computers and modems e. g. was originally drafted as a recommended standard, thus the " RS " RS-232.

On traditional minicomputers, the console was a serial console, an RS-232 serial link to a terminal such as a DEC VT100.

The connection between the computer and the communications medium was generally implemented through an RS-232 interface, or something similar.

On PCs, 25-pin and ( beginning with the IBM-PC / AT ) 9-pin plugs are used for the RS-232 serial ports ; 25-pin sockets are used for the parallel printer ports ( instead of the Centronics socket found on the printer itself which was inconveniently large for direct placement on the expansion cards ).

The name stems from the historical use of the RS-232 cable to connect two teleprinter devices to modems in order to communicate with one another ; null modem communication was possible by instead using RS-232 to connect the teleprinters directly to one another.

Originally, the RS-232 standard was developed and used for teleprinter machines which could communicate with each other over phone lines.

It was typical for the Q line to drive a status LED, a cassette interface, an RS-232 interface, and the speaker.

Less common for machines in its class was the integrated RS-232 serial port, which allowed the MC-10 to use a wide variety of line printers and modems without additional hardware.

The numerous external ports ( by the standards of the time ), including the standard RS-232 on the 64, also allows hobbyists to attach a diverse range of equipment.

A D-subminiature | DB-25 connector as described in the RS-232 standard

However, the limited transmission speed, relatively large voltage swing, and large standard connectors motivated development of the universal serial bus, which has displaced RS-232 from most of its peripheral interface roles.

Since the requirements of devices such as computers, printers, test instruments, POS terminals and so on were not considered by the standard, designers implementing an RS-232 compatible interface on their equipment often interpreted the requirements idiosyncratically.

The standard has been renamed several times during its history as the sponsoring organization changed its name, and has been variously known as EIA RS-232, EIA 232, and most recently as TIA 232.

Issues with the RS-232 standard include:

However, USB is limited by standard to no more than 5 meters of cable, thus favoring RS-232 when longer distances are needed.

USB is more complex than the RS-232 standard because it includes a protocol for transferring data to devices.

The RS-232 standard defines the voltage levels that correspond to logical one and logical zero levels for the data transmission and the control signal lines.

External RS-232 / 485 converters or internal RS-485 cards have to be installed as standard PCs do not have RS-485 communication ports.

While the RS-232 standard originally specified a 25-pin D-type connector, many designers of personal computers chose to implement only a subset of the full standard: they traded off compatibility with the standard against the use of less costly and more compact connectors ( in particular the DE-9 version used by the original IBM PC-AT ).

When using asynchronous serial communication such as standard RS-232 serial ports, bits are sent in groups of 8, and bit-stuffing is inconvenient.

For this purpose, a paperclip is used to short pin 2 to pin 3 ( the receive and transmit pins ) on a standard RS-232 interface using D-subminiature DE-9 or DB-25 connectors.

The widest application of D-subs is for RS-232 serial communications, though the standard did not make this connector mandatory.

The RS-232 standard is asymmetrical as to the definitions of the two ends of the communications link so it assumes that one end is a DTE and the other is a DCE e. g. a modem.