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

16

4.6 CMX969 Modem Tasks

4.6.1 Transmit Mode

CMX969 Advance Information

B2 B1 B0

RD-LAP

0 0 0 NULL

0 0 1 T24S Transmit 24 symbols

0 1 0 THB

Transmit Header Block

0 1 1 TIB

Transmit Intermediate Block

1 0 0 TLB

Transmit Last Block

1 0 1 T4S

Transmit 4 symbols

1 1 0 TSID

Transmit Station ID

1 1 1 RESET Cancel any current action

NULL

T40B

THB

TIB

TLB

T8B

-

RESET

MDC

Transmit 40 bits

Transmit Header Block

Transmit Intermediate Block

Transmit Last Block

Transmit 8 bits

Unused

Cancel any current action

When the modem is in transmit mode, all tasks other than NULL or RESET instruct the modem to transmit

data from the Data Buffer, formatting it as required. The µC should therefore wait until the BFREE (Buffer

Free) bit of the Status Register is '1', before writing the data to the Data Block Buffer, then it should write the

desired task to the Command Register. If more than 1 byte needs to be written to the Data Block Buffer, byte

number 0 of the block should be written first.

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

Set the BFREE (Buffer Free) bit of the Status Register to '0'.

Take the data from the Data Block Buffer as quickly as it can - transferring it to the Interleave Buffer

for eventual transmission. This operation will start immediately if the modem is 'idle' (i.e. not

transmitting data from a previous task), otherwise it will be delayed until there is sufficient room in the

Interleave Buffer.

Once all of the data has been transferred from the Data Block Buffer, the modem will set the BFREE

and IRQ bits of the Status Register to '1' (causing the chip IRQ output to go low if the IRQEN bit of

the Mode Register has been set to '1'). This tells the µC that it may write new data and the next task

to the modem.

This lets the µC write a task and the associated data to the modem while the modem is still transmitting the

data from the previous task.

Data from µC to Block Buffer

Task from µC to Command Register

Task 1

BFREE bit of Status Register

Task 2

IRQ bit of Status Register

IRQ output (IRQEN = '1')

TXOUT signal

from task 1

from task 2

Figure 9: Transmit Task Overlapping

¤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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