{"id":3808,"date":"2018-08-28T11:39:59","date_gmt":"2018-08-28T16:39:59","guid":{"rendered":"https:\/\/www.westfloridacomponents.com\/blog\/?p=3808"},"modified":"2018-02-27T11:40:45","modified_gmt":"2018-02-27T16:40:45","slug":"rs232-rs485-different","status":"publish","type":"post","link":"https:\/\/www.westfloridacomponents.com\/blog\/rs232-rs485-different\/","title":{"rendered":"How are RS232 and RS485 Different?"},"content":{"rendered":"

When engineers need to connect electronic equipment, they resort to serial interfaces such as the RS-232 and RS-485. Although dozens of other serial data interfaces exist today, most are meant for use in specific applications. A few of them are considered universal, such as I2S, MOST, FLEX, SPI, LIN, CAN and I2C. Other high-speed serial interfaces are also used, including Thunderbolt, HDMI, FireWire, USB, and Ethernet. Despite the proliferation of interfaces, the two legacy interfaces, RS-232 and RS-485, continue to survive, used in several applications<\/span>.<\/span><\/p>\n

As a rule, serial interfaces provide a single path for data to be transmitted over a cable or wirelessly. Although some applications do use parallel buses, serial interface alone provides the only practical option for high-speed data movement today over any distance greater than several feet.<\/span><\/p>\n

RS-232<\/b><\/span><\/p>\n

RS-232 is one of the oldest serial interfaces, originally established in 1962, as a method of connecting a DTE or data terminal equipment such as a teletypewriter to a DCE or data communications equipment. Personal computers earlier had an RS-232 port, commonly called the serial port, to connect to a printer or other peripheral device. Embedded computer development systems still use the port today, as do many scientific instruments, and several industrial control equipment.<\/span><\/p>\n

Officially, the standard defining the RS-232 serial interface is the EIA\/TIA-232-F, with F signifying the most recent update. According to the standard, a logic 1 is defined as a voltage between -3 and -25 V, and a logic 0 as a voltage between +3 and +25 V. The logic 1 is generally termed as a mark, with logic 0 being termed as a space. Any voltage between +3 and -3 V is termed invalid and is rejected, providing a huge noise margin for the interface. The configurations of the receiver and transmitter are both single-ended and referenced to ground or 0 V.<\/span><\/p>\n

The cable medium in RS-232 can be simple wires in parallel or a twisted pair. According to the standard, the cable length must not exceed 50 feet. However, by reducing the data rate, it is possible to use longer lengths of cable. For a 50-foot cable, the highest data rates in RS-232 are roughly 20 Kbits\/s, and matched generator and load impedances are necessary for eliminating reflections and data corruption. Although earlier 25-pin connectors were used, the de-facto standard for RS-232 is the 9-pin DE-9 connector today.<\/span><\/p>\n

RS-485<\/b><\/span><\/p>\n

The EIA\/TIA standards also define the RS-485 interface, now commonly known as TIA-485. This is not only a single device-device interface, but is a complete communication bus used for simple networking of multiple devices.<\/span><\/p>\n

Rather than a single-ended voltage referenced to the ground, the RS-485 uses differential signaling on two lines. A logic 1 is a voltage level greater than 200 mV, while the logic 0 is a level greater than +200 mV. The maximum cable length for RS<\/span>–<\/span>485 is about 4000 feet or 1200 m, with typical data rates as 100 Kbits\/s. However, compared to the speed of the RS-232 interface, a 20-meter cable in RS-485 can allow a maximum data rate of 5Mbits\/s. Industrial control equipment using the RS-485 use the 9-pin DE-9 connector.<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

When engineers need to connect electronic equipment, they resort to serial interfaces such as the RS-232 and RS-485. Although dozens of other serial data interfaces exist today, most are meant for use in specific applications. A few of them are considered universal, such as I2S, MOST, FLEX, SPI, LIN, CAN and I2C. Other high-speed serial […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[15],"tags":[1986,1307],"class_list":["post-3808","post","type-post","status-publish","format-standard","hentry","category-guides","tag-rs-232","tag-rs-485"],"_links":{"self":[{"href":"https:\/\/www.westfloridacomponents.com\/blog\/wp-json\/wp\/v2\/posts\/3808"}],"collection":[{"href":"https:\/\/www.westfloridacomponents.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.westfloridacomponents.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.westfloridacomponents.com\/blog\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.westfloridacomponents.com\/blog\/wp-json\/wp\/v2\/comments?post=3808"}],"version-history":[{"count":1,"href":"https:\/\/www.westfloridacomponents.com\/blog\/wp-json\/wp\/v2\/posts\/3808\/revisions"}],"predecessor-version":[{"id":3809,"href":"https:\/\/www.westfloridacomponents.com\/blog\/wp-json\/wp\/v2\/posts\/3808\/revisions\/3809"}],"wp:attachment":[{"href":"https:\/\/www.westfloridacomponents.com\/blog\/wp-json\/wp\/v2\/media?parent=3808"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.westfloridacomponents.com\/blog\/wp-json\/wp\/v2\/categories?post=3808"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.westfloridacomponents.com\/blog\/wp-json\/wp\/v2\/tags?post=3808"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}