Communication protocol – ACS ACR38K Smart Keyboard User Manual
Page 10
ACR38x (CCID) – Reference Manual
Version 6.04
www.acs.com.hk
Page 10 of 58
7.0. Communication Protocol
ACR38x (CCID) 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 ACR38x (CCID) 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 ACR38x (CCID)
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 ACR38x (CCID) have
to be sent synchronously (e.g., bMaxCCIDBusySlots is equal to 01h for ACR38x (CCID)).
The ACR38x (CCID) 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 ACR38x (CCID).
5
bVoltageSupport
1
ACR38x (CCID) can supply 1.8 V, 3 V, and
5 V to its slot.
6
dwProtocols
4
ACR38x (CCID) supports T=0 and T=1
protocol.
10
dwDefaultClock
4
Default ICC clock frequency is 4 MHz.
14
dwMaximumClock
4
Maximum supported ICC clock frequency
is 4 MHz.
18
bNumClockSupported
1
Does not support manual setting of clock
frequency.
19
dwDataRate
4
Default ICC I/O data rate is 10752 bps.
23
dwMaxDataRate
4
Maximum supported ICC I/O data rate is
344 kbps.
27
bNumDataRatesSupported
1
Does not support manual setting of data
rates.
28
dwMaxIFSD
4
Maximum IFSD supported by ACR38x
(CCID) for protocol T=1 is 254.
32
dwSynchProtocols
4
ACR38x (CCID) does not support
synchronous card.
36
dwMechanical
4
ACR38x (CCID) does not support special
mechanical characteristics.