824
11054A–ATARM–27-Jul-11
SAM9X25
824
11054A–ATARM–27-Jul-11
SAM9X25
Figure 39-29.
Connection of a Smart Card to the USART
When operating in ISO7816, either in T = 0 or T = 1 modes, the character format is fixed. The
configuration is 8 data bits, even parity and 1 or 2 stop bits, regardless of the values pro-
grammed in the CHRL, MODE9, PAR and CHMODE fields. MSBF can be used to transmit LSB
or MSB first. Parity Bit (PAR) can be used to transmit in normal or inverse mode. Refer to
“USART Mode Register” on page 858
and
“PAR: Parity Type” on page 859
.
The USART cannot operate concurrently in both receiver and transmitter modes as the commu-
nication is unidirectional at a time. It has to be configured according to the required mode by
enabling or disabling either the receiver or the transmitter as desired. Enabling both the receiver
and the transmitter at the same time in ISO7816 mode may lead to unpredictable results.
The ISO7816 specification defines an inverse transmission format. Data bits of the character
must be transmitted on the I/O line at their negative value. The USART does not support this for-
mat and the user has to perform an exclusive OR on the data before writing it in the Transmit
Holding Register (US_THR) or after reading it in the Receive Holding Register (US_RHR).
39.7.4.2
Protocol T = 0
In T = 0 protocol, a character is made up of one start bit, eight data bits, one parity bit and one
guard time, which lasts two bit times. The transmitter shifts out the bits and does not drive the
I/O line during the guard time.
If no parity error is detected, the I/O line remains to 1 during the guard time and the transmitter
can continue with the transmission of the next character, as shown in
.
If a parity error is detected by the receiver, it drives the I/O line to 0 during the guard time, as
shown in
. This error bit is also named NACK, for Non Acknowledge. In this case,
the character lasts 1 bit time more, as the guard time length is the same and is added to the
error bit time which lasts 1 bit time.
When the USART is the receiver and it detects an error, it does not load the erroneous character
in the Receive Holding Register (US_RHR). It appropriately sets the PARE bit in the Status Reg-
ister (US_SR) so that the software can handle the error.
Figure 39-30.
T = 0 Protocol without Parity Error
Smart
Card
SCK
CLK
TXD
I/O
USART
D0
D1
D2
D3
D4
D5
D6
D7
RXD
Parity
Bit
Baud Rate
Clock
Start
Bit
Guard
Time 1
Next
Start
Bit
Guard
Time 2
Содержание SAM9X25
Страница 26: ...26 11054A ATARM 27 Jul 11 SAM9X25...
Страница 138: ...138 11054A ATARM 27 Jul 11 SAM9X25 138 11054A ATARM 27 Jul 11 SAM9X25...
Страница 162: ...162 11054A ATARM 27 Jul 11 SAM9X25 162 11054A ATARM 27 Jul 11 SAM9X25...
Страница 216: ...216 11054A ATARM 27 Jul 11 SAM9X25 216 11054A ATARM 27 Jul 11 SAM9X25...
Страница 266: ...266 11054A ATARM 27 Jul 11 SAM9X25 266 11054A ATARM 27 Jul 11 SAM9X25...
Страница 330: ...330 11054A ATARM 27 Jul 11 SAM9X25 330 11054A ATARM 27 Jul 11 SAM9X25...
Страница 374: ...374 11054A ATARM 27 Jul 11 SAM9X25...
Страница 468: ...468 11054A ATARM 27 Jul 11 SAM9X25 468 11054A ATARM 27 Jul 11 SAM9X25...
Страница 532: ...532 11054A ATARM 27 Jul 11 SAM9X25 532 11054A ATARM 27 Jul 11 SAM9X25...
Страница 692: ...692 11054A ATARM 27 Jul 11 SAM9X25 692 11054A ATARM 27 Jul 11 SAM9X25...
Страница 777: ...777 11054A ATARM 27 Jul 11 SAM9X25 777 11054A ATARM 27 Jul 11 SAM9X25...
Страница 886: ...886 11054A ATARM 27 Jul 11 SAM9X25 886 11054A ATARM 27 Jul 11 SAM9X25...
Страница 962: ...962 11054A ATARM 27 Jul 11 SAM9X25 962 11054A ATARM 27 Jul 11 SAM9X25...
Страница 1036: ...1036 11054A ATARM 27 Jul 11 SAM9X25 1036 11054A ATARM 27 Jul 11 SAM9X25...
Страница 1067: ...1067 11054A ATARM 27 Jul 11 SAM9X25 1067 11054A ATARM 27 Jul 11 SAM9X25 PTZ Pause Time Zero Enable pause time zero interrupt...
Страница 1069: ...1069 11054A ATARM 27 Jul 11 SAM9X25 1069 11054A ATARM 27 Jul 11 SAM9X25 PTZ Pause Time Zero Disable pause time zero interrupt...
Страница 1071: ...1071 11054A ATARM 27 Jul 11 SAM9X25 1071 11054A ATARM 27 Jul 11 SAM9X25 PTZ Pause Time Zero Pause time zero interrupt masked...
Страница 1128: ...1128 11054A ATARM 27 Jul 11 SAM9X25 1128 11054A ATARM 27 Jul 11 SAM9X25...
Страница 1130: ...1130 11054A ATARM 27 Jul 11 SAM9X25...
Страница 1131: ...1131 11054A ATARM 27 Jul 11 SAM9X25 Revision History Doc Rev 11054A Comments Change Request Ref 1st issue...
Страница 1132: ...1132 11054A ATARM 27 Jul 11 SAM9X25...
Страница 1144: ...xii 11054A ATARM 27 Jul 11 SAM9X25...