ACR3901T-W1 – Reference Manual
Version 1.02
www.acs.com.hk
Page 37 of 100
6.2. USB Communication Protocol
The ACR3901T-W1 shall interface with the host through the USB connection. A specification, namely
CCID, has been released within the industry defining such a protocol for the USB chip-card interface
devices. CCID covers all the protocols required for operating smart cards.
The configurations and usage of USB endpoints on ACR3901T-W1 shall follow CCID Rev 1.0 Section
3.
An overview is summarized below:
1.
Control Commands
are sent on control pipe (default pipe). These include class-specific
requests and USB standard requests. Commands that are sent on the default pipe report
information back to the host on the default pipe.
2.
CCID Events
are sent on the interrupt pipe.
3.
CCID Commands
are sent on BULK-OUT endpoint. Each command sent to ACR3901T-W1
has an associated ending response. Some commands can also have intermediate responses.
4.
CCID Responses
are sent on BULK-IN endpoint. All commands sent to ACR3901T-W1 have
to be sent synchronously (e.g.,
bMaxCCIDBusySlots
is equal to 01h for ACR3901T-W1).
The ACR3901T-W1 supported CCID features are indicated in its Class Descriptor:
Offset
Field
Size Value Description
0
bLength
1
-
Size of this descriptor, in bytes
1
bDescriptorType
1
-
CCID Functional Descriptor type
2
bcdCCID
2
-
CCID Specification Release Number in
Binary-coded decimal
4
bMaxSlotIndex
1
-
One slot is available on ACR3901T-W1
5
bVoltageSupport
1
-
ACR3901T-W1 can supply 1.8 V, 3 V, and
5 V to its slot
6
dwProtocols
4
-
ACR3901T-W1 supports T=0 and T=1
protocol
10
dwDefaultClock
4
-
Default ICC clock frequency is 4.8 MHz
14
dwMaximumClock
4
-
Maximum supported ICC clock frequency
is 4.8 MHz
18
bNumClockSupported
1
-
Does not support manual setting of clock
frequency
19
dwDataRate
4
-
Default ICC I/O data rate is 12903 bps
23
dwMaxDataRate
4
-
Maximum supported ICC I/O data rate is
600 Kbps
27
bNumDataRatesSupported
1
-
Does not support manual setting of data
rates
28
dwMaxIFSD
4
-
Maximum IFSD supported by ACR3901T-
W1 for protocol T=1 is 254
32
dwSynchProtocols
4
-
ACR3901T-W1
does not support
synchronous card
36
dwMechanical
4
-
ACR3901T-W1 does not support special
mechanical characteristics
