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SmartCard Interface Module (SIM)
25.8.6 Automatic Receiver Mode
The SIM has an automatic receive mode that inhibits the data being transmitted by the SIM from entering
the SIM receive buffer through the feedback path of the SIM data pin. The SIM receiver should normally
be enabled while the transmitter is operational. Automatic receive mode saves the software from having to
actively manage the transition from transmitter to receiver. The auto receive mode is always active
whenever the receiver is enabled.
25.8.7 Using the SIM Receiver with T = 1 SmartCards
The SIM provides hardware support for T = 1 type SmartCards. These type of cards present several
requirements above and beyond the standard T = 0 cards. The features provided to meet the requirements
that pertain to the SIM receiver are as follows:
•
11 ETU Characters
— T = 1 cards can transmit with character lengths of 11 ETUs (one STOP bit). The SIM provides
the RCVR11 bit in the GUARD_CNTL register to configure the receiver state machine to
accept 11 ETU characters.
•
Character Wait Time Counter
— The character waiting time (CWT) is defined as the time between the start bits of two
consecutive characters. The value of CWT can range from 12 ETUs to 32779 ETUs. The SIM
provides a 16-bit counter with programmable comparator clocked at the ETU bit rate to identify
when the CWT has been exceeded by the SmartCard.
•
Block Waiting Time
— The block waiting time (BWT) is defined as the time between the start bits of the last character
of a received block and the first character of the next received block. The value of BWT is
always greater than 1800 ETUs. The SIM provides a 16-bit general purpose counter that can
identify when the BWT has been exceeded by the SmartCard. For detecting BWT violations,
the general purpose counter can be configured to be clocked at the ETU bit rate. A 16-bit
comparator is provided to generate an interrupt when the BWT has expired.
•
Block Guard Time
— The block guard time (BGT) is defined as the minimum delay between the leading edges of two
consecutive characters sent in opposite directions. The value of BGT is 22 ETUs. The SIM
supports the BGT by providing the ability to generate an interrupt when the last byte is received,
and transmitting within 2 ETUs after the XMT_EN bit in the ENABLE register is set. The BGT
is determined by the speed at which the software can react to an interrupt and enable the
transmitter. Again, the general purpose counter can guarantee that the software does not violate
the BGT.
•
Error Detection Code
— T = 1 cards can specify the use of LRC or CRC error detection codes. The SIM provides
hardware support for both the LRC and CRC operations.
25.9 Using the SIM Transmitter
After the SIM has been properly configured (data XMT enabled, correct baud rate, correct data format, and
so on), the transmitter can be enabled by setting the XMT_EN bit in the ENABLE register. When data had
been previously written to the transmit FIFO, the transmitter begins to send the first character. When no
data is written to the transmit FIFO before enabling the transmitter, then the transmitter waits until the first
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MC9328MX1 Reference Manual
MOTOROLA
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