IBM 3270: Семейство терминалов и принтеров с блочной ориентацией.

Family of block oriented display terminals and printers made by IBM

The IBM 3270 is a family of block oriented display and printer computer terminals introduced by IBM in 1971 and normally used to communicate with IBM mainframes. The 3270 was the successor to the IBM 2260 display terminal. Due to the text color on the original models, these terminals are informally known as green screen terminals. Unlike a character oriented terminal, the 3270 minimizes the number of I/O interrupts required by transferring large blocks of data known as data streams, and uses a high speed proprietary communications interface, using coaxial cable. IBM no longer manufactures 3270 terminals, but the IBM 3270 protocol is still commonly used via TN3270 clients, 3270 terminal emulation or web interfaces to access mainframe based applications, which are sometimes referred to as green screen applications.

The 3270 series was designed to connect with mainframe computers, often at a remote location, using the technology then available in the early 1970s. Originally devices were connected to the control unit over coaxial cable; later Token Ring, twisted pair, or Ethernet connections were available. A local control unit attaches directly to the channel of a nearby mainframe. A remote control unit is connected to a communications line by a modem. Remote 3270 controllers are frequently multi dropped, with multiple control units on a line. IBM 3270 devices are connected to a 3299 multiplexer or to the cluster controller, e. g., 3271, 3272, 3274, 3174, using RG 62, 93 ohm, coax cables in a point to point configuration with one dedicated cable per terminal. Data is sent with a bit rate of 2.3587 Mbit/s using a slightly modified differential Manchester encoding. Cable runs of up to are supported, although IBM documents routinely stated the maximum supported coax cable length was 609.60 m. Originally devices were equipped with BNC connectors, which later was replaced with special so called DPC – Dual Purpose Connectors supporting the IBM Shielded twisted pair cabling system without the need for so called red baluns. In a data stream, both text and control (or formatting functions) are interspersed allowing an entire screen to be painted as a single output operation. The concept of formatting in these devices allows the screen to be divided into fields (clusters of contiguous character cells) for which numerous field attributes, e. g., color, highlighting, character set, protection from modification, can be set. A field attribute occupies a physical location on the screen that also determines the beginning and end of a field. There are also character attributes associated with individual screen locations. Using a technique known as read modified, a single transmission back to the mainframe can contain the changes from any number of formatted fields that have been modified, but without sending any unmodified fields or static data. This technique enhances the terminal throughput of the CPU, and minimizes the data transmitted. Some users familiar with character interrupt driven terminal interfaces find this technique unusual. There is also a read buffer capability that transfers the entire content of the 3270 screen buffer including field attributes. This is mainly used for debugging purposes to preserve the application program screen contents while replacing it, temporarily, with debugging information. Early 3270s offered three types of keyboards. The typewriter keyboard came in both a 66 key version, with no programmed function (PF) keys, and a 78 key version with twelve. Both versions had two Program Attention (PA) keys. The data entry keyboard had five PF keys and two PA keys. The operator console keyboard had twelve PF keys and two PA keys. IBM and third party software that included an interactive component took for granted the presence of 3270 terminals and provided a set of ISPF panels and supporting programs. Conversational Monitor System (CMS) in VM has support for the 3270 continuing to z/VM. Time Sharing Option (TSO) in OS/360 and successors has line mode command line support and also has facilities for full screen applications, e. g., ISPF. Device independent Display Operator Console Support (DIDOCS) in Multiple Console Support (MCS) for OS/360 and successors supports 3270 devices and, in fact, MCS in current versions of MVS no longer supports line mode, 2250 and 2260 devices. The SPF and Program Development Facility (ISPF/PDF) editors for MVS and VM/SP (ISPF/PDF was available for VM, but little used) and the XEDIT editors for VM/SP through z/VM make extensive use of 3270 features. Customer Information Control System (CICS) has support for 3270 panels. Indeed, from the early 1970s on, CICS applications were often written for the 3270. Later an Operator Identification Card Reader was added which could read information encoded on a magnetic stripe card.

Generally, 3277 models allow only upper case input, except for the mixed EBCDIC/APL or text keyboards, which have lower case. Lower case capability and dead keys were available as an RPQ (Request Price Quotation); these were added to the later 3278 & 3279 models. A version of the IBM PC called the 3270 PC, released in October 1983, includes 3270 terminal emulation. Later, the 3270 PC/G (graphics), 3270 PC/GX (extended graphics), 3270 Personal Computer AT, 3270 PC AT/G (graphics) and 3270 PC AT/GX (extended graphics) followed.

There are two types of 3270 displays in respect to where the 3270 data stream terminates. For CUT (Control Unit Terminal) displays, the stream terminates in the display controller, the controller instructs the display to move the cursor, position a character, etc. EBCDIC is translated by the controller into '3270 Character Set', and keyboard scan codes from the terminal, read by the controller through a poll, is translated by the controller into EBCDIC. For DFT (Distributed Function Terminal) type displays, most of the 3270 data stream is forwarded to the display by the controller. The display interprets the 3270 protocol itself. In addition to passing the 3270 data stream directly to the terminal, allowing for features like EAB Extended Attributes, Graphics, etc., DFT also enabled multi sessions (up to 5 simultaneous), featured in the 3290 and 3194 multisession displays. This feature was also widely used in 2nd generation 3270 terminal emulation software. The MLT Multiple Logical Terminals feature of the 3174 controller also enabled multiple sessions from a CUT type terminal. + CUT vs. DFT Display Station Name CUT vs. DFT 3178 all models CUT 3179 Model 1 CUT 3179 Models G1, G2 DFT 3180 Model 1 CUT 3191 all models CUT 3192 Models C, D, F, L, W CUT 3192 Model G DFT 3193 all models DFT 3194 all models DFT 3277 all models CUT 3278 all models CUT 3279 all models CUT 3290 all models DFT3472 except model GCUT3472 model GDFT3482 all modelsDFT

The 3290 Information Panel a 17", amber monochrome plasma display unit announced March 8, 1983, capable of displaying in various modes, including four independent 3278 model 2 terminals, or a single 160×62 terminal; it also supports partitioning. The 3290 supports graphics through the use of programmed symbols. A 3290 application can divide its screen area up into as many as 16 separate explicit partitions (logical screens). The 3290 is a Distributed Function Terminal (DFT) and requires that the controller do a downstream load (DSL) of microcode from floppy or hard disk.

The 3180 was a monochrome display, introduced on March 20, 1984, that the user could configure for several different basic and extended display modes; all of the basic modes have a primary screen size of 24x80. Modes 2 and 2+ have a secondary size of 24x80, 3 and 3+ have a secondary size of 32x80, 4 and 4+ have a secondary size of 43x80 and 5 and 5+ have a secondary size of 27x132. An application can override the primary and alternate screen sizes for the extended mode. The 3180 also supported a single explicit partition that could be reconfigured under application control.

The IBM 3191 Display Station is an economical monochrome CRT. Models A and B are 1920 characters 12 inch CRTs. Models D, E and L are 1920 or 2560 character 14 inch CRTs.

The IBM 3193 Display Station is a high resolution, portrait type, monochrome, 380mm (15 inch) CRT image display providing up to letter or A4 size document display capabilities in addition to alphanumeric data. Compressed images can be sent to the 3193 from a scanner and decompression is performed in the 3193. Image data compression is a technique to save transmission time and reduce storage requirements.

Several third party manufacturers produced 3270 displays besides IBM.

GTE manufactured the IS/7800 Video Display System, nominally compatible with IBM 3277 displays attached to a 3271 or 3272. An incompatibility with the RA buffer order broke the logon screen in VM/SE (SEPP).

Informer Computer Terminals manufactured a special version of their model 270 terminal that was compatible with IBM 3270 and its associated coax port to connect to a 3x74.

AT&T introduced the Dataspeed 40 terminal/controller, compatible with the IBM 3275, in 1980.

IBM had two different implementations for supporting graphics. The first was implemented in the optional Programmed Symbol Sets (PSS) of the 3278, 3279 and 3287, which became a standard feature on the later 3279 S3G, a. k. a. 3279G, and was based on piecing together graphics with on the fly custom defined symbols downloaded to the terminal. The second later implementation provided All Points Addressable (APA) graphics, a. k. a. Vector Graphics, allowing more efficient graphics than the older technique. The first terminal to support APA / Vector graphics was the 3179G terminal that later was replaced by first the 3192G and later the 3472G. Both implementations are supported by IBM GDDM Graphical Data Display Manager first released in 1979, and by SAS with their SAS/GRAPH software.

IBM 3279 S3G, a. k. a. 3279G, terminal, announced in 1979, was IBM's graphics replacement for the 3279 3B with PSS. The terminal supported 7 colors and the graphics were made up of Programmable Symbol sets loaded to the terminal by the graphical application GDDM Graphical Data Display Manager using Write Structured Field command. Programmable Symbols is an addition to the normal base character set consisting of Latin characters, numbers, etc. hardwired into the terminal. The 3279G supports six additional sets of symbols each supporting 190 symbols, resulting in a total of 1.140 programmable symbols. Three of the Programmable Symbols sets have three planes each enabling coloring (red, blue, green) the Programmable Symbols downloaded to those sets, thereby supporting a total of seven colors. Each 'character' cell consists of a 9x12 or a 9x16 dot matrix depending on the screen model. In order to program a cell with a symbol 18 bytes of data is needed making the data load quite heavy in some instances when compared to classic text screens. If one for example wishes to draw a hyperbola on the screen, the application must first compute the required Programmable Symbols to make up hyperbola and load them to the terminal. The next step is then for the application to paint the screen by addressing the screen cell position and select the appropriate symbol in one of the Programmable Symbols sets. The 3279G could be ordered with Attribute Select Keyboard enabling the operator to select attributes, colors and Programmable Symbols sets, making that version of the terminal quite distinctive.

The IBM 3179G announced June 18, 1985, is an IBM mainframe computer terminal providing 80×24 or 80×32 characters, 16 colors, plus graphics and is the first terminal to support the APA graphics apart from the 3270 PC/G, 3270 PC/GX, PC AT/G and PC AT/GX. 3179 G terminals combine text and graphics as separate layers on the screen. Although the text and graphics appear combined on the screen, the text layer actually sits over the graphics layer. The text layer contains the usual 3270 style cells which display characters (letters, numbers, symbols, or invisible control characters). The graphics layer is an area of 720×384 pixels. All Points Addressable or vector graphics is used to paint each pixel in one of sixteen colors. As well as being separate layers on the screen, the text and graphics layers are sent to the display in separate data streams, making them completely independent. The application i. e. GDDM sends the vector definitions to the 3179 G, and the work of activating the pixels that represent the picture (the vector to raster conversion) is done in the terminal itself. The datastream is related to the number of graphics primitives (lines, arcs, and so on) in the picture. Arcs are split into short vectors, that are sent to the 3179 G to be drawn. The 3179 G does not store graphic data, and so cannot offload any manipulation function from GDDM. In particular, with user control, each new viewing operation means that the data has to be regenerated and retransmitted. The 3179G is a distributed function terminal (DFT) and requires a downstream load (DSL) to load its microcode from the cluster controller's floppy disk or hard drive. The G10 model is a standard 122 key typewriter keyboard, while the G20 model offers APL on the same layout. Compatible with IBM System/370, IBM 4300 series, 303x, 308x, IBM 3090, and IBM 9370.

The IBM 3192G, announced in 1987 was the successor to 3179G. It featured 16 colors, and support for printers (i. e., IBM Proprinter) for local hardcopy with graphical support, or system printer, text only, implemented as an additional LU.

The IBM 3472G announced in 1989 was the successor to 3192G and featured five concurrent sessions, one of which could be graphics. Unlike the 3192 G, it needed no expansion unit to attach a mouse or color plotter, and it could also attach a tablet device for digitised input and a bar code reader.

Most IBM terminals, starting with the 3277, could be delivered with an APL keyboard, allowing the operator/programmer to enter APL symbolic instructions directly into the editor. In order to display APL symbols on the terminal, it had to be equipped with an APL character set in addition to the normal 3270 character set. The APL character set is addressed with a preceding Graphic Escape X'08' instruction. With the advent of the graphic terminal 3179G, the APL character set was expandable to 138 characters, called APL2. The added characters were: Diamond, Quad Null, Iota Underbar, Epsilon Underbar, Left Tack, Right Tack, Equal Underbar, Squished Quad, Quad Slope, and Dieresis Dot. Later APL2 symbols were supported by 3191 Models D, E, L, the CUT version of 3192, and 3472. Please note that IBM's version's of APL also is called APL2.

IBM introduced the 3174 Subsystem Control Unit in 1986, replacing the 3274 product line. The 3174 was designed to enhance the 3270 product line with many new connectivity options and features. Like the 3274, it was customizable, the main difference was that it used smaller (5.25 inch) diskettes than the 3274 (8 inch diskettes), and that the larger floor models had 10 slots for adapters, some of them were per default occupied by channel adapter/serial interface, coax adapter, etc. Unlike the 3274, any local models could be configured as either local SNA or local non SNA, including PU2.1 (APPN). The models included: 01L, 01R, 02R, 03R, 51R, 52R, 53R, 81R and 82R. The 01L were local channel attached, the R models remotely connected, and the x3R Token Ring (upstream) connected. The 0xL/R models were floor units supporting up to 32 coax devices through the use of internal or external multiplexers (TMA/3299). The 5xR, models were shelf units with 9 coax ports, expandable to 16, by the connection of a 3299 multiplexer. The smallest desktop units, 8xR, had 4 coax ports expandable to 8, by the connection of a 3299 multiplexer. In the 3174 controller line IBM also slightly altered the classical BNC coax connector by changing the BNC connector to DPC – Dual Purpose Connector. The DPC female connector was a few millimeters longer and with a built in switch that detected if a normal BNC connector were connected or a newer DPC connector was connected, thereby changing the physical layer from 93 ohm unbalanced coax, to 150 ohm balanced twisted pair, thereby directly supporting the IBM Cabling system without the need for a so called red balun. Configuration Support A was the first microcode offered with the 3174. It supported all the hardware modules present at the time, almost all the microcode features found in 3274 and introduced a number of new features including: Intelligent Printer Data Stream (IPDS), Multiple Logical Terminals, Country Extended Code Page (CECP), Response Time Monitor, and Token Ring configured as host interface. Configuration Support S, strangely following release A, introduced that a local or remote controller could act as 3270 Token Ring DSPU Gateway, supporting up to 80 Downstream PU's. In 1989, IBM introduced a new range of 3174 models and changed the name from 3174 Subsystem Control Unit to 3174 Establishment Controller. The main new feature was support for an additional 32 coax port in floor models. The models included: 11L, 11R, 12R, 13R, 61R, 62R, 63R, 91R, and 92R. The new line of controllers came with Configuration Support B release 1, increased the number of supported DSPU on the Token Ring gateway to 250 units, and introduced at the same time 'Group Polling' that offloaded the mainframe/VTAM polling requirement on the channel. Configuration Support B release 2 to 5, enabled features like: Local Format Storage (CICS Screen Buffer), Type Ahead, Null/Space Processing, ESCON channel support. In 1990–1991, a total of 7 more models were added: 21R, 21L, 12L, 22L, 22R, 23R, and 90R. The 12L offered ESCON fibreoptic channel attachment. The models with 2xx designation were equal to the 1xx models but repacked for rackmount and offered only 4 adapter slots. The 90R was not intended as a coax controller, it was positioned as a Token Ring 3270 DSPU gateway. However, it did have one coax port for configuring the unit, which with a 3299 multiplexer could be expanded to 8. The line of controllers came with Configuration Support C to support ISDN, APPN and Peer Communication. The ISDN feature allowed downstream devices, typically PC's, to connect to the 3174 via the ISDN network. The APPN support enabled the 3174 to be a part of an APPN network, and the Peer Communication allowed coax attached PC's with 'Peer Communication Support' to access resources on the Token Ring network attached to the 3174. The subsequent releases 2 to 6 of Configuration Support C enables support for: Split screen, Copy from session to session, Calculator function, Access to AS/400 host and 5250 keyboard emulation, Numerous APPN enhancements, TCP/IP Telnet support that allowed 3270 CUT terminals to communicate with TCP/IP servers using Telnet, and at the same time in another screen to communicate with the mainframe using native 3270. TN3270 support where the 3174 could connect to a TN3270 host/gateway, eliminating SNA, but preserving the 3270 data stream. IP forwarding allowing bridging of LAN (Token Ring or Ethernet) connected devices downstream to the 3174 to route IP traffic onto the Frame Relay WAN interface. In 1993, three new models were added with the announcement of Ethernet Adapter (FC 3045). The models were: 14R, 24R, and 64R. This was also IBM's final hardware announcement of 3174. The floor models, and the rack mountable units, could be expanded with a range of special 3174 adapters, that by 1993 included: Channel adapter, ESCON adapter, Serial (V.24/V.35) adapter, Concurrent Communication Adapter, Coax adapter, Fiber optic "coax" adapter, Async adapter, ISDN adapter, Token Ring adapter, Ethernet adapter, and line encryption adapter. In 1994, IBM incorporated the functions of RPQ 8Q0935 into Configuration Support C release 3, including the TN3270 client.

An alternative implementation of an establishment controller exists in form of OEC (Open Establishment Controller). It's a combination of an Arduino shield with a BNC connector and a Python program that runs on a POSIX system. OEC allows to connect a 3270 display to IBM mainframes via TN3270 or to other systems via VT100. Currently only CUT but not DFT displays are supported.

IBM offered a device called 3299 that acted as a multiplexer between an accordingly configured 3274 controller, with the 9901 multiplexer feature, and up to eight displays/printers, thereby reducing the number of coax cables between the 3x74 controller and the displays/printers. With the introduction of the 3174 controller internal or external multiplexers (3299) became mainstream as the 3174 1L controller was equipped with four multiplexed ports each supporting eight devices. The internal 3174 multiplexer card was named TMA – Terminal Multiplexer adapter 9176. A number of vendors manufactured 3270 multiplexers before and alongside IBM including Fibronics and Adacom offering multiplexers that supported TTP – Telephone Twisted Pair as an alternative to coax, and fiber optic links between the multiplexers. In some instances, the multiplexer worked as an "expansion" unit on smaller remote controllers including the 3174 81R / 91R, where the 3299 expanded the number of coax ports from four to eight, or the 3174 51R / 61R, where the 3299 expanded the number of coax ports from eight to 16.

The IBM 3270 display terminal subsystem was designed and developed by IBM's Kingston, New York, laboratory (which later closed during IBM's difficult time in the mid 1990s). The printers were developed by the Endicott, New York, laboratory. As the subsystem expanded, the 3276 display controller was developed by the Fujisawa laboratory, Japan, and later the Yamato laboratory; and the 3279 color display and 3287 color printer by the Hursley, UK, laboratory. The subsystem products were manufactured in Kingston (displays and controllers), Endicott (printers), and Greenock, Scotland, UK, (most products) and shipped to users in U. S. and worldwide. 3278 terminals continued to be manufactured in Hortolândia, near Campinas, Brazil as far as late 1980s, having its internals redesigned by a local engineering team using modern CMOS technology, while retaining its external look and feel.

Telnet 3270, or tn3270 describes both the process of sending and receiving 3270 data streams using the telnet protocol and the software that emulates a 3270 class terminal that communicates using that process. tn3270 allows a 3270 terminal emulator to communicate over a TCP/IP network instead of an SNA network. Telnet 3270 can be used for either terminal or print connections. Standard telnet clients cannot be used as a substitute for tn3270 clients, as they use fundamentally different techniques for exchanging data.

The 3270 displays are available with a variety of keyboards and character sets. The following table shows the 3275/3277/3284–3286 character set for US English EBCDIC (optional characters were available for US ASCII, and UK, French, German, and Italian EBCDIC). On the 3275 and 3277 terminals without the a text feature, lower case characters display as uppercase. NL, EM, DUP, and FM control characters display and print as 5, 9, *, and ; characters, respectively, except by the printer when WCC or CCC bits 2 and 3 = '00'b, in which case NL and EM serve their control function and do not print.

Data sent to the 3270 consist of commands, a Copy Control Character (CCC) or Write Control Character (WCC) if appropriate, a device address for copy, orders, character data and structured fields. Commands instruct the 3270 control unit to perform some action on a specified device, such as a read or write. Orders are sent as part of the data stream to control the format of the device buffer. Structured fields are to convey additional control functions and data to or from the terminal. On a local non SNA controller, the command is a CCW opcode rather than the first byte of the outbound display stream; on all other controllers, the command is the first byte of the display stream, exclusive of protocol headers.

The following table includes datastream commands and CCW opcodes for local non SNA controllers; it does not include CCW opcodes for local SNA controllers. +3270 commands Command HexadecimalGraphic Function localnon SNA EBCDIC ASCII Copy F7 37 7 Copy from one device buffer to another, e. g., from a display to a printer Erase All Unprotected 0F 6F 3F ? Erase all unprotected fields and reset modified data tags Erase/Write 05 F5 35 5 Erase device buffer, then write WCC folloed by orders and data Erase/Write Alternate 0D 7E 3D = Erase device buffer, set alternate size, then write WCC folloed by orders and data No Operation 03 May be used to retrieve pending status Read Buffer 02 F2 22 2 Read entire device buffer, including attributes Read Modified 06 F6 36 6 Read AID, cursor and, except for short read, modified fields from device Read Modified All 6E 3E : Read AID, cursor and modified fields from device; no short read Select 0B Transfer data from device to control unit with channel disconnected Select RB 1B Select Read Buffer;may only be chained to Read Buffer Select RBP 3B Select Read Buffer from Position;may only be chained to Read Buffer Select RM DB Select Read Modified Select RMP 2B Select Read Modified from Position Select WRT 4B Select WRT CommandMay only be chained to a Write or Write Structured Field Sense 04 Retrieve error information after unit check Sense ID E4 Retrieve control unit identification Write 01 F1 31 1 Write WCC followed by orders and data Write Structured Field 11 F3 3 Write Structured Field For remote 3270s non significant bits are set so that the command forms a valid EBCDIC (or ASCII) character.

The data sent by Write or Erase/Write consists of the command code itself followed by a Write Control Character (WCC) optionally followed by a buffer containing orders or data (or both). The WCC controls the operation of the device. Bits may start printer operation and specify a print format. Other bit settings will sound the audible alarm if installed, unlock the keyboard to allow operator entry, or reset all the Modified Data Tags in the device buffer.

The 3278 and 3279 and later models used extended attributes to add support for seven colors, blinking, reverse video, underscoring, field outlining, field validation, and programmed symbols.

The 3278 and 3279 and later models allowed attributes on individual characters in a field to override the corresponding field attributes. This allowed programs (such as the LEXX text editor) to assign any font (including the programmable fonts), colour, etc. to any character on the screen.

3270 displays and printers have a buffer containing one byte for every screen position. For example, a 3277 model 2 featured a screen size of 24 rows of 80 columns for a buffer size of 1920 bytes. Bytes are addressed from zero to the screen size minus one, in this example 1919. "There is a fixed relationship between each buffer storage location and its position on the display screen." Most orders start operation at the "current" buffer address, and executing an order or writing data will update this address. The buffer address can be set directly using the Set Buffer Address (SBA) order, often followed by Start Field or Start Field Extended. For a device with a 1920 character display a twelve bit address is sufficient. Later 3270s with larger screen sizes use fourteen or sixteen bits. Addresses are encoded within orders in two bytes. For twelve bit addresses the high order two bits of each byte are set to form valid EBCDIC (or ASCII) characters. For example, address 0 is coded as X'4040', or space space, address 1919 is coded as X'5D7F', or ''. Programmers hand coding panels usually keep the table of addresses from the 3270 Component Description or the 3270 Reference Card handy. For fourteen and sixteen bit address, the address uses contiguous bits in two bytes.