FX929AD2 datasheet(16/44 Pages) CMLMICRO

16 / 44 page

4-Level FSK Modem Data Pump

FX929A

D/929A/4

When the modem is in receive mode, the µC should wait until the BFREE bit of the Status Register is '1', then

write the desired task to the Command Register.

Once the byte containing the desired task has been written to the Command Register, the modem will:

Set the BFREE bit of the Status Register to '0'.

Wait until enough received symbols are in the De-interleave Buffer.

Decode them as needed, and transfer the resulting binary data to the Data Block Buffer

Then the modem will set the BFREE and IRQ bits of the Status Register to '1', (causing the IRQN

output to go low if the IRQNEN bit of the Mode Register has been set to '1') to tell the µC that it may

read from the Data Block Buffer and write the next task to the modem. If more than 1 byte is contained

in the buffer, byte number 0 of the data will be read out first.

In this way the µC can read data and write a new task to the modem while the received symbols needed for this

new task are being received and stored in the De-interleave Buffer.

BFREE bit of Status Register

for task 1

for task 2

RXIN signal

Task 1

Task 2

Task 1 data

Data from Block Buffer to µC

Task from µC to Command Register

IRQN o/p (IRQNEN = '1')

IRQ bit of Status Register

Figure 9 Receive Task Overlapping

Detailed timings for the various tasks are given in Figures 10 and 11.

FX929A Modem Tasks:

Receive Mode

Transmit Mode

NULL

SFP

Search for Frame Preamble

T24S

Transmit 24 symbols

RHB

Read Header Block

THB

Transmit Header Block

RILB

Read Intermediate or Last

Block

TIB

Transmit Intermediate Block

SFS

Search for Frame Sync

TLB

Transmit Last Block

R4S

Read 4 symbols

T4S

Transmit 4 symbols

RSID

Read Station ID

TSID

Transmit Station ID

RESET

Cancel any current action

RESET

Cancel any current action

NULL: No effect

This task is provided so that a AQSC or AQLEV command can be initiated without loading a new task.

FX929AD2 Datasheet(PDF) 16 Page - CML Microcircuits

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