DS8007 Datasheet, PDF (35/41 Pages) Dallas Semiconductor – Multiprotocol Dual Smart Card Interface

Multiprotocol Dual Smart Card Interface
Character Encoding/
Decoding Convention
The ISO UART is designed to support two possible char-
acter encoding/decoding formats: direct and inverted.
The direct character coding convention transmits and
receives data LSb first and associates a high logic level
with a bit 1 and a low logic level with a bit 0. The inverse
character coding convention transmits and receives data
most significant bit first and associates a high logic level
with a bit 0 and a low logic level with a bit 1.
The UCR1.CONV bit defines which character conven-
tion (CONV = 0:inverse; CONV = 1:direct) should be
used by the ISO UART. The UCR1.CONV bit can be
configured by the host device software or be config-
ured by hardware if automatic convention detection has
been enabled.
Automatic Convention Detection
The automatic convention detection relies upon recog-
nition of a predefined pattern in the first character
received (TS character) in ATR for establishing future
character coding convention. To enable automatic con-
vention detection, the UCR1.SS bit must be set to logic
1 and the UCR2.AUTOC bit should be configured to
logic 0 prior to ATR. The SS bit is automatically cleared
by hardware 10.5 ETU after the character is received. If
automatic convention detection is enabled and an
unrecognized character is received, the CONV bit is
not written. If neither the direct nor inverse character
are detected, a parity error occurs along with error sig-
nal generation for the T = 0 protocol. The AUTOC bit
should not be modified during a card session.
Framing Error Detection
The DS8007 monitors the selected card I/Ox signal at
10.25 ETU following each detected start bit. If the I/Ox
signal is not in the high state at this point in time, the
USR.FER (framing error) bit is set to 1 at 10.5 ETU. The
FER bit is cleared to 0 whenever USR is read.
TS CHARACTER
(CONVEYS CODING CONVENTION)
DIRECT CONVENTION (BYTE = 3Bh)
110 11 10 01
LSb
MSb
INVERSE CONVENTION (BYTE = 3Fh)
001 11 11 10
MSb
LSb
Figure 12. Direct, Inverse Character Coding Conventions
ISO UART
I/OA
I/OB
I/OAUX
f_CLKx
2 x f_CLKx
START DETECT
ETU
URR
FIFO(8)
UTR
PDR.PD[7:0]
GTR.GTR.[7:0]
UCR1
UCR2
CSR.RIU
MSR.FER
MSR.BGT
MSR.TBE/RBF
USR.EA
USR.PE
USR.OVR
USR.FER
FCR.PEC[2:0]
FCR.FL[2:0]
Figure 13. ISO UART Signal Interface
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