provide configuration options that exceed the flexibility of
options explicitly allowed by the 7816 specification. Failure to
correctly configure the UART may result in unexpected
behavior or incompatibility with the ISO-7816 specification.
38.5.7.1 Initial characters
In ISO-7816 with T = 0 mode, the UART can be configured to use C7816[INIT] to detect
the next valid initial character, referred to by the ISO-7816 specifically as a TS character.
When the initial character is detected, the UART provides the host processor with an
interrupt if IE7816[INITDE] is set. Additionally, the UART will alter S2[MSBF],
C3[TXINV], and S2[RXINV] automatically, based on the initial character. The
corresponding initial character and resulting register settings are listed in the following
table.
Table 38-12. Initial character automated settings
Initial character (bit 1-10)
Initial character
(hex)
MSBF
TXINV
RXINV
LHHL LLL LLH
inverse convention
3F
1
1
1
LHHL HHH LLH
direct convention
3B
0
0
0
S2[MSBF], C3[TXINV], and S2[RXINV] must be reset to their default values before
C7816[INIT] is set. Once C7816[INIT] is set, the receiver searches all received data for
the first valid initial character. Detecting a Direct Convention Initial Character will cause
no change to S2[MSBF], C3[TXINV], and S2[RXINV], while detecting an Inverse
Convention Initial Character will cause these fields to set automatically. All data
received, which is not a valid initial character, is ignored and all flags resulting from the
invalid data are blocked from asserting. If C7816[ANACK] is set, a NACK is returned
for invalid received initial characters and an RXT interrupt is generated as programmed.
38.5.7.2 Protocol T = 0
When T = 0 protocol is selected, a relatively complex error detection scheme is used.
Data characters are formatted as illustrated in the following figure. This scheme is also
used for answer to reset and Peripheral Pin Select (PPS) formats.
Chapter 38 Universal Asynchronous Receiver/Transmitter(UART)
KL27 Sub-Family Reference Manual , Rev. 5, 01/2016
Freescale Semiconductor, Inc.
731
Содержание MKL27Z128VFM4
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