Rainbow Electronics AT89C5122 - Manual (Page 71)

71
AT8xC5122/23
4202E–SCR–06/06
Figure 35. T=0 mode
In T=1 protocol : The maximum interval between the leading edge of the start bit of 2
consecutive 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. Con-
sequently 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 leading 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. Con-
sequently 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 characters, and the ICC is supposed to respond immediately after, then the follow-
ing sequence can be used.
Wh ile sending the (N-1)th chara cter 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 36. T=1 Mode
CHAR 1 CHAR 2
< WT
> GT
BLOC 1
CHAR 1 CHAR 2 CHAR n
BLOC 2
CHAR n+1 CHAR n+2 CHAR n+3
< BWT
< CWT
TRANSMISSION RECEPTION