CMX969P4 查看數據表（PDF） - MX-COM Inc

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CMX969P4

MOTIENT/ARDIS RD-LAP MDC4800 Modem

MX-COM Inc  

MOTIENTSM/ARDISSM RD-LAPTM MDC4800 Modem

19

4.6.2 Receive Mode:

CMX969 Advance Information

B2 B1 B0

RD-LAP

0 0 0 NULL

0 0 1 SFP

Search for Frame Preamble

0 1 0 RHB

Read Header Block

0 1 1 RILB

Read Intermediate or Last

Block

1 0 0 SFS

Search for Frame Sync

1 0 1 R4S

Read 4 symbols

1 1 0 RSID Read Station ID

1 1 1 RESET Cancel any current action

NULL

-

RHB

RILB

SFS

R8B

-

RESET

MDC

Unused

Read Header Block

Read Intermediate or Last

Block

Search for Frame Sync

Read 8 bits

Unused

Cancel any current action

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 IRQ

output to go low if the IRQEN 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.

RXIN signal

IRQ output (IRQEN = '1')

IRQ bit of Status Register

for task 1

for task 2

BFREE bit of Status Register

Task from µC to Command Register

Data from Block Buffer to µC

Task 1

Task 2

Task 1 data

Figure 10: Receive Task Overlapping

Detailed timings for the various tasks are given in Figure 11 and Figure 12.

4.6.2.1 NULL:

This ‘task’ allows the AFSD or RXEYE bits to be changed without any other effect.

¤2001 MX-COM, Inc.

www.mxcom.com Tel: 800 638 5577 336 744 5050 Fax: 336 744 5054

Doc. # 20480211.002

4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA All trademarks and service marks are held by their respective companies.

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