FX909AD2 Просмотр технического описания (PDF) - CML Microsystems Plc

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FX909AD2

Wireless Modem Data Pump

CML Microsystems Plc 

Wireless Modem Data Pump

FX909A

RSB - Read Single Byte

This task causes the modem to read the next 8 bits and translate them directly (without de-

interleaving or FEC) to an 8-bit byte which is placed into the Data Buffer (B7 will represent the

earliest bit received). The BFREE and IRQ bits of the Status Register will then be set to '1' to indicate

that the µC may read the data byte from the Data Buffer and write the next task to the Command

Register.

This task is intended for special tests and channel monitoring - perhaps preceded by an SFS task.

LFSB - Load Frame Sync Bytes

This task takes 2 bytes from the Data Buffer and updates the Frame Sync detect bytes. The MSB of

byte '0' is compared to the first bit of a received Frame Sync pattern and the LSB of byte '1' is

compared to the last bit of a received Frame Sync pattern. This task does not enable Frame Sync

detection.

Unlike other Rx tasks, the data buffer must be loaded before the task is issued and the task must

only be issued 'between' received messages, i.e. before the first task for receiving a message and

after the last data is read out of the data buffer.

Once the modem has read the Frame Sync bytes from the Data Buffer, the BFREE and IRQ bits of

the Status Register will be set to '1', indicating to the µC that it may write the next task to the modem.

T7H - Transmit 7-byte Frame Head

This task takes 6 bytes of data from the Data Buffer, calculates and appends 8 bits of FEC from

bytes '4' and '5' then transmits the result as a complete Mobitex Frame Head.

Bytes '0' and '1' form the bit sync pattern, bytes '2' and '3' form the frame sync pattern and bytes '4'

and '5' are the frame head control bytes. Bit 7 of byte '0' of the Data Buffer is sent first, bit 0 of the

FEC byte last.

Once the modem has read the data bytes from the Data Buffer, the BFREE and IRQ bits of the

Status Register will be set to '1', indicating to the µC that it may write the next task and its data to the

modem.

TQB - Transmit 4 Bytes

This task takes 4 bytes of data from the Data Buffer and transmits them, bit 7 first.

Once the modem has read the data bytes from the Data Buffer, the BFREE and IRQ bits of the

Status Register will be set to '1', indicating to the µC that it may write the next task and its data to the

modem.

TDB - Transmit Data Block

This task takes 18 bytes of data from the Data Buffer, calculates and applies a 16-bit CRC and forms

the FEC for the 18 data bytes and the CRC. This data is then interleaved and passed through the

scrambler, if enabled, before being transmitted as a Mobitex Data Block.

Once the modem has read the data bytes from the Data Buffer, the BFREE and IRQ bits of the

Status Register will be set to '1', indicating to the µC that it may write the next task and its data to the

modem.

Note: In transmit mode the CRC checksum circuit is initialised on completion of any task other than

NULL.

© 1996 Consumer Microcircuits Limited

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D/909A/4

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