MX809

The MX809 is an intelligent, half-duplex 1200-baud MSK Modem, which operates under C-BUS control. This modem provides software selectable checksum generation and error checking in accordance with MPT1327.

In TX Mode the MX809 will:

1. a) Accept from the host and transmit 8-bit bytes of data as instructed (preamble, sync, address, and data), or b) Internally calculate and inset a 2 byte checksum based on the preceding 6 bytes f data, or c) Disable the internal checksum generator and continuously transmit the data supplied.

2. Transmit 1 hang-bit and go to TX idle when all loaded data bytes have been transmitted.

In RX Mode the MX809 will:

1. Detect and carry out bit synchronization within 16 bits.

2. a) Search and detect the user-programmed Sync (or its opposite logic sense) Word and carry out frame synchronization. Data will then be output in 8-bit bytes via the RX Data Buffer.

b) Use the received checksum to calculate the presence of any errors, setting the Status Register accordingly.

3. Make the incoming data directly available via the RX Data Buffer (RX Freeformat), overriding the synchronization requirements.

RX input timing is achieved by recovering an RX clock from the incoming data stream. Output tones are timed to the internally generated TX clock. Filter, register clocks, and transmit MSK tone frequencies are derived internally from the external Xtal or clock pulse input.

A 4.032MHz Xtal or clock input is required for compliance with the MPT1327 Signaling Specification. Note: All information contained in this data bulletin is specified using a 4.032MHz Xtal, 1200bps baud rate, with Mark and Space frequencies of 1200Hz and 1800Hz. The MX809 has a non-committed amplifier on-chip for general applications in the DBS 800 series.

The MX809 may be used with a 5.0V power supply and is available in the following packages: 24-pin PLCC (MX809LH), and 24-pin CERDIP (MX809J).