AT90SCR100 datasheet(184/433 Pages) ATMEL

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TPR0327AY–SMS–30Jan09

AT90SCR100

Figure 15-6.

T=0 mode

In T=1 protocol : The maximum interval between the leading edge of the start bit of 2 consecu-

tive characters sent by the ICC is called maximum Character Waiting Time. The Character

Waiting Time shall not exceed (2*CWI + 11) ETUs with 0 =< BWI =< 5. Consequently 12 ETUs

=< CWT =< 43 ETUs.

T=1 protocol also specify the maximum Block Waiting Time. This is the time between the leading

edge of the last character sent by the Terminal giving the right to send to the ICC, and the lead-

ing edge of the start bit of the first character sent by the ICC. The Block Waiting Time shall not

exceed (2*BWI*960 + 11) ETUs with 0 =< BWI =< 4. Consequently 971 ETUs =< BWT =< 15371

ETUs.

In T=1 protocol it is possible to extend the Block Waiting Time with the Waiting Time Extension

(WTX). When selected the waiting time becomes BWT*WTX ETUs. The Waiting Time counter is

32 bit wide to accomodate this feature.

It is possible to take advantage of the automatic reload of the Waiting Time counter with a start

bit in UART mode (T=1 protocol use UART mode) . If the Terminal sends a block of N charac-

ters, and the ICC is supposed to answer immediately after, then the following sequence can be

used.

While sending the (N-1)th character of the block, the Terminal can write the SCWT0,1,2,3 with

BWImax.

At the start bit of the Nth character, the BWImax is loaded in the Waiting Time counter

During the transmission of the Nth character, the Terminal can write SCWT0,1,2,3 with the

CWImax.

At the start bit of the first character sent by the ICC, the CWImax will be loaded in the Waiting

Time counter.

Figure 15-7.

T=1 Mode

CHAR 1

CHAR 2

> GT

< WT

CHAR 1

CHAR 2

CHAR n

Bloc 1

TRANSMISSION

CHAR 1

CHAR 2

CHAR n

< BWT

Bloc n

RECEPTION

< CWT

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