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MT8982AS Datasheet(PDF) 3 Page - Mitel Networks Corporation |
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MT8982AS Datasheet(HTML) 3 Page - Mitel Networks Corporation |
3 / 19 page ISO-CMOS MT8982 2-33 Functional Description The MT8982 (MiniDX) provides cost effective time switching capability for small size applications utilizing up to two serial Time Division Multiplexed (TDM) streams. Each TDM stream consists of 32 64 kb/s channels, giving the MiniDX a maximum capacity of 64 channels. The input framing signal may be either a ST-BUS or a GCI frame pulse. The MT8982 will output a delayed or advanced frame pulse in the opposite format to permit conversion between the two formats. The MiniDX can switch data from any channel in one of the two serial input TDM streams to any channel in either of the two serial output TDM streams. The microcontroller controlling the MiniDX writes to the MT8982 Connect Memory to establish the connection between the required input TDM channel and the selected output TDM channel(s). By reading the Connect Memory the microcontroller can check switched connections which have already been established. The MiniDX can also operate in message mode where the microcontroller transmits the data on the TDM serial stream. The microcontroller writes to the MT8982 Connect Memory to transmit data on the required output TDM channels. Reading the Data Memory of the MT8982 allows the microcontroller to receive messages from TDM input channels. These operations are useful for control of other ST-BUS components or for interprocessor communication. Hardware Description TDM Interface The MT8982 continuously receives TDM serial data at 2048 kbit/s through two serial inputs. These serial streams are then converted into a parallel format and stored sequentially in a 64x8 bit Data Memory. The sequential addressing is generated by an internal counter that is reset by the input 8 kHz frame pulse (F0i) which marks the frame boundaries of the incoming serial data stream. This counter increments with each timeslot so that it matches the binary count of the timeslot of the incoming data. The TDM timeslot count always corresponds to the ST-BUS channel positions. An extra address bit is used to differentiate between the two input data streams. The input 8 kHz frame pulse may be either ST-BUS or GCI formatted. A ST-BUS formatted frame pulse is an active low signal which straddles the frame boundary. It idles high the rest of the time. A GCI formatted frame pulse is active high at the beginning of timeslot 5 (relative to the MT8982) and idles low. The MT8982 automatically determines the type of frame pulse from the level of the idle over five clock periods. A ST-BUS formatted frame pulse resets the internal address counters to zero. A GCI formatted frame pulse resets the counters to five. F0o outputs a frame pulse in the opposite format. If F0i is a ST-BUS formatted frame pulse, F0o will be a GCI formatted frame pulse delayed by five channels after F0i. If F0i is a GCI formatted frame pulse, F0o will be a ST-BUS formatted frame pulse delayed by 27 channels (32-5). During normal operation every second falling edge of the clock marks a timeslot boundary and the input data is clocked in by the rising edge, three-quarters of the way into the bit cell. The master clock must be 4.096 MHz for the F0o signal to be valid and to receive a GCI formatted F0i. Data which is output onto a TDM serial output channel may come from two sources; the Data Memory or the Connect Memory. If a channel is configured in connection mode, the source of output data is the Data Memory. If a channel is configured in message mode, the source of the output data is the Connect Memory. Data destined for a particular channel on the serial output links is read from the data or connect memory in the previous channel timeslot. This allows for delay in RAM access and parallel-to-serial conversion. Each output data channel can also be placed in tristate mode. When an output channel is in connection mode, the TDM output data is read from a Data Memory location pointed to by an address stored in the 64x8 bit Connect Memory. The Connect Memory locations are addressed sequentially, with each location corresponding to an output TDM link/ channel. In the channel time before the data is to be output, the contents of each Connect Memory location are output to the address bus of the Data Memory. The contents of the Data Memory at the selected address are then transferred to the parallel- to-serial converter. The parallel-to-serial converter outputs onto the TDM serial stream during the correct channel time. By having the output channel specify the input channel, the user can route the same input channel to several output channels. This function is useful for broadcasting or resource channel uses. |
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