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The UART will automatically handle GT, CGT, and BGT such that the UART will not
send a packet before the corresponding guard time expiring.
Table 38-13. Wait and guard time calculations
Parameter
Reset value
[ETU]
C7816[TTYPE] = 0
[ETU]
C7816[TTYPE] = 1
[ETU]
Wait time (WT)
9600
WI × 480
Not used
Character wait time (CWT)
Not used
Not used
2
(CWI1)
+ CWI2
Block wait time (BWT)
Not used
Not used
(11 + (BWI × 960 × GTFD)) * (WTX
+ 1)
Guard time (GT)
12
GTN not equal to 255
12 + GTN
GTN equal to 255
12
Not used
Character guard time (CGT)
Not used
Not used
GTN not equal to 255
12 + GTN
GTN equal to 255
11
Block guard time (BGT)
Not used
Not used
16 + BGI
NOTE
• User must ensure that the Character Wait time (CWT)
programmed using the formula above is atleast 12. Values
smaller than 12 are invalid and will lead to unexpected
CWT interrupts.
• The 16 bit Wait Time integer WI is formed by
concatenation of {WP7816A_T0[WI_H],
WP7816B_T0[WI_L]}.
• The 16 bit Block Wait Time integer BWI is formed by
concatenation of {WP7816A_T1[BWI_H],
WP7816B_T1[BWI_L]}.
38.5.7.5 ATR Duration Time Counter
The ISO-7816 specification defines a specific time (in etus) within which the terminal
must receive the ATR (Answer to Reset), failing which the terminal must abort the card
session by initiating the deactivation sequence.
UART supports this in hardware via the ATR Duration Time (ATD) Counter which can
be programmed using AP7816a_T0 and AP7816b_T0 registers. The value loaded into the
ADT (ATR Duration Time) counter is given by the concatenation of the register fields as
Functional description
KL27 Sub-Family Reference Manual , Rev. 5, 01/2016
734
Freescale Semiconductor, Inc.