ACR39x – Reference Manual
Version 1.03
www.acs.com.hk
Page 7 of 35
4.0. USB Interface
4.1. Communication Parameters
The ACR39x is connected to a computer through USB as specified in the USB Specification 2.0. The
ACR39x is working in full speed mode, i.e. 12 Mbps.
Pin
Signal
Function
1
V
BUS
+5 V power supply for the reader
2
D-
Differential signal transmits data between ACR39x and computer
3
D+
Differential signal transmits data between ACR39x and computer
4
GND
Reference voltage level for power supply
Table 2
: USB Interface Wiring
4.2. Endpoints
The ACR39x uses the following endpoints to communicate with the host computer:
Control Endpoint
For setup and control purpose.
Bulk-OUT
For command to be sent from host to ACR39x.
(Data packet size is 64 bytes)
Bulk-IN
For response to be sent from ACR39x to host.
(Data packet size is 64 bytes)
Interrupt-IN
For card status message to be sent from ACR39x to host.
(Data packet size is 8 bytes)
