ACR39x – Reference Manual
Version 1.03
www.acs.com.hk
Page 10 of 35
7.0. USB Communication Protocol
ACR39x 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 ACR39x 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 ACR39x 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 ACR39x have to be
sent synchronously (e.g.,
bMaxCCIDBusySlots
is equal to 01h for ACR39x).
The ACR39x 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 ACR39x.
5
bVoltageSupport
1
ACR39x can supply 1.8 V, 3 V, and 5 V to
its slot.
6
dwProtocols
4
ACR39x 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 12918 bps.
23
dwMaxDataRate
4
Maximum supported ICC I/O data rate is
826 Kbps.
27
bNumDataRatesSupported
1
Does not support manual setting of data
rates.
28
dwMaxIFSD
4
Maximum IFSD supported by ACR39x for
protocol T=1 is 247.
32
dwSynchProtocols
4
ACR39x does not support synchronous
card.
36
dwMechanical
4
ACR39x does not support special
mechanical characteristics.
