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MT8920BP Datasheet(PDF) 4 Page - Mitel Networks Corporation |
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MT8920BP Datasheet(HTML) 4 Page - Mitel Networks Corporation |
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4 / 29 page  MT8920B CMOS 3-6 Functional Description The STPA (ST-BUS Parallel Access) device provides a simple interface between Mitel’s ST-BUS and parallel system environments. The ST-BUS is a synchronous, time division, multiplexed serial bussing scheme with data streams operating at 2048 kbit/s. The ST-BUS is the primary means of access for voice, data and control information to Mitel’s family of digital telecommunications components, including North American and European digital trunk interfaces, ISDN U and S digital line interfaces, filter codecs, rate adapters, etc. The STPA provides several modes of operation optimized according to the type of information being handled. For interfacing parallel data and control information to the ST-BUS, such as signalling and link control for digital trunks, the STPA provides a µP access mode (Mode 1), and looks like a 68000 type peripheral. In this mode, the device provides powerful interrupt features, useful in monitoring digital trunk or line status (i.e., synchronization, alarms, etc.) or for setting up message communication links between microprocessors. To interface high speed data or multi-channel voice/ data to the ST-BUS for switching or transmission, the STPA has a high speed synchronous access mode (Mode 2) and acts like a fast RAM. For voice storage and forward, bulk data transfer, data buffering and other similar applications, the STPA has a controllerless mode (Mode 3) in which it provides address and control signals to the parallel bus This is useful for performing direct transfers to the ST-BUS from external devices such as a RAM buffer. The STPA is a two port device as shown in the functional block diagram in Figure 1. The parallel port provides direct access to three dual port RAM’s, two transmit and one receive. The address, data and control busses are used to communicate between the RAM‘s and a parallel environment. Two parallel-to-serial converters, and one serial-to-parallel converter interface the dual port RAM’s to the ST-BUS port of the STPA. This port consists of two serial output streams and one serial input stream operating at 2048 kbit/s. This configuration of two outputs and one input was designed to allow a single STPA to form a complete control interface to Mitel’s digital trunk interfaces (MT8976, MT8978 and MT8979) which have two serial input and one serial output control streams. ST-BUS clocking circuitry, address generator and various control and interrupt registers complete the STPA’s functionality. Modes of Operation The three basic modes of operation, µP Peripheral Mode (Mode 1), Fast RAM Mode (Mode 2) and Bus Controller Mode (Mode 3) are selected using two external input pins. These inputs are MMS and MS1 and are decoded as shown in Table 1. Whenever MMS=1 the device resides in Mode 1. In this mode, MS1 pin is unavailable and is used for a different function. When MMS=0, Modes 2 or 3 are selected as determined by input MS1. If MS1=1, Mode 2 is selected and if MS1 =0, Mode 3 is selected. Each of the modes of the STPA provides a different pinout to ease interfacing requirements of different parallel environments. These are shown in Figure 3 below. In µP Peripheral Mode the device uses interface signals consistent with a 68000-type µP bus. Mode 2, Fast RAM Mode, uses signals typical of standard RAM type interfaces. Mode 3 interface signals are very similiar to Mode 2 signals except that the address and control signals are supplied as outputs by the STPA. Figure 3 - Modes 1, 2, 3 Pin Connections µP Peripheral Mode #1 Fast RAM 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 28 27 26 25 24 23 22 21 C4i F0i IACK STi0 CS DS R/W A0 A1 A2 A3 A4 A5 VSS VDD MMS DTACK IRQ STo1 STo0 D7 D6 D5 D4 D3 D2 D1 D0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 28 27 26 25 24 23 22 21 C4i F0i MS1 STi0 CS OE R/W A0 A1 A2 A3 A4 A5 VSS VDD MMS BUSY 24/32 STo1 STo0 D7 D6 D5 D4 D3 D2 D1 D0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 28 27 26 25 24 23 22 21 C4i F0i MS1 STi0 CS OE WE A0 A1 A2 A3 A4 STCH VSS VDD MMS DCS 24/32 STo1 STo0 D7 D6 D5 D4 D3 D2 D1 D0 Mode #2 Bus Controller Mode #3 |
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Similar Description - MT8920BP |
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