AN93

For Figure 39, assume that the originating modem transmits first and that the two modems alternate transmitting and receiving. For simplicity, this figure does not show the provisions for timeout cases.

 

 

 

 

 

 

HES = 1

 

 

 

 

 

 

AT+FCLASS = 256

 

 

 

 

 

 

(V .2 3 half -duple x )

 

 

 

 

ATDTxxxx ;

 

O

Orig ina te

A

 

 

 

 

 

?

ATDT ;

 

 

 

 

 

 

 

 

 

 

OK

 

 

 

OK

 

 

1

Pr otocol

2

 

 

AT +FRM =200

 

 

 

?

 

 

 

 

 

 

 

 

 

 

 

 

AT+FTM =201

 

 

AT + FTM = 202

 

 

 

 

 

 

 

 

CONNECT n

 

 

CONNECT

 

 

CONNEC T

n = 1 o r 2

 

N

Data received

 

N

Data received

 

 

 

from Host

 

 

from Host

Receive messag e ,

 

 

?

 

 

?

 

 

 

 

 

 

send to Host

 

 

 

 

 

 

 

 

 

Y

 

 

Y

 

 

 

 

80 bits of mark

 

 

30 0 bits channel

 

 

 

 

 

 

seizure

 

 

 

 

 

 

 

( alternating

1 's &

OK

 

 

Host sends

 

 

0's)

 

 

 

 

 

 

 

 

 

 

 

message followed

 

 

 

 

 

 

 

by 15 0 ms o f

 

 

 

 

 

 

 

silence , then ESC

 

 

80 bits of mark

 

 

 

 

 

 

Host sends

 

 

N

ESC to

 

 

message followed

 

Send Marks

 

 

by 15 0 ms of

 

Command

 

 

 

 

 

 

silence , then ESC

 

 

 

Mod e

 

 

 

 

 

 

 

 

 

 

 

 

?

 

 

 

 

 

 

 

Y

 

 

 

 

 

 

 

 

 

N

ESC to

 

 

 

 

 

 

 

 

 

 

 

 

Send Marks

 

Command

 

 

 

 

 

 

Mode

 

 

 

 

 

 

 

?

 

 

 

 

 

 

 

Y

 

Implicit +FRM

Figure 39. SMS Process in Host and Modem

Rev. 1.3

241

Page 241
Image 241
Silicon Laboratories SI2494/39, SI2493/57/34/15/04 manual SMS Process in Host and Modem