1 INTRODUCTION
The Quatech MPA-200/300 is a single channel, synchronous serial communica- tion port for systems utilizing the architecture of the IBM AT personal or compati- ble computers. The MPA-200 is RS-422 compatible.
The MPA-300 has RS-485 data line drivers and receivers in place of the MPA-200's RS-422 drivers and receivers. The MPA-300's RS-485 interface will allow multiple systems to be connected in a multi-drop configuration. Hereafter, the MPA-200 and MPA-300 will be collectively referred to as the MPA-200 except where noted.
The ports of the MPA-200 occupy an 8 byte block of I/O address space. The base address of this block may be located anywhere within the available I/O address space of the system.
The MPA-200 is available with a variety of serial communications controlers (SCC). All of the available SCC's can support asynchronous formats, byte- oriented protocols such as IBM Bisync, and bit-oriented protocols such as HDLC and IBM SDLC. The SCC's also offer internal functions such as on-chip baud rate generators, and digital phase-lock loops (DPLL).
The MPA-200 also supports Direct Memory Access (DMA) and interrupts. DMA channels 1 - 3 can be used for high data transfer rates, while interrupt levels 2 - 7, 10 - 12, and 14 - 15 are available for several interrupt sources.
On the MPA-200, communications is controlled by the SCC labeled U17. There are seven jumper blocks on the MPA-200 that allow the user to select such options as DMA channels, interrupt levels and driver control. If the MPA-200 is configured for data terminal equipment (DTE), external connections are made through a male D-25 connector CN2. If the MPA-200 is configured for data communications equipment (DCE), external connections are made through a a female D-25 connector CN1. These configurations are determined when the board is manufactured, prior to shipment.
On the MPA-200, the driver circuit consists of one RS-422 driver (U18), one RS-422 receiver (U26), four RS-422/485 transceivers (U19, U20, U22, U23), two RS-423 drivers (U24, U25). Each differential pair that is received by the MPA-200 has a 100 ohm termination resistor.
On the MPA-300, the driver circuit consists of one RS-485 driver (U19), one RS-485 receiver (U26), four RS-422/485 transceivers (U19, U20, U22, U23), two RS-423 drivers (U24, U25). Each differential pair that is received by the MPA-300 has a 150 ohm termination resistor.
