EZ-USB Datasheet, PDF (236/334 Pages) Cypress Semiconductor – The EZ-USB USB Integrated Circuit

USBPAIR
b7
b6
ISOSEND0
-
R/W
R/W
0
x
USB Endpoint Pairing
b5
PR6OUT
R/W
0
b4
PR4OUT
R/W
0
b3
PR2OUT
R/W
0
b2
PR6IN
R/W
0
Figure 12-35. USB Endpoint Pairing Register
b1
PR4IN
R/W
0
7FDD
b0
PR2IN
R/W
0
Bit 7:
ISOSEND0 Isochronous Send Zero Length Data Packet
The ISOSEND0 bit is used when the EZ-USB chip receives an isochronous IN token
while the IN FIFO is empty. If ISOSEND0=0 (the default value), the EZ-USB core does
not respond to the IN token. If ISOSEND0=1, the EZ-USB core sends a zero-length data
packet in response to the IN token. Which action to take depends on the overall system
design. The ISOSEND0 bit applies to all of the isochronous IN endpoints, IN8BUF
through IN15BUF.
Bit 5-3:
PRnOUT Pair Bulk OUT Endpoints
Set the endpoint pairing bits (PRxOUT) to “1” to enable double-buffering of the bulk
OUT endpoint buffers. With double buffering enabled, the 8051 can operate on one buffer
while another is being transferred over USB. The endpoint busy and interrupt request bits
function identically, so the 8051 code requires no code modification to support double
buffering.
When an endpoint is paired, the 8051 uses only the even-numbered endpoint of the pair.
The 8051 should not use the paired odd endpoint’s IRQ, IEN, VALID bits or the buffer
associated with the odd numbered endpoint.
Bit 2-0:
PRnIN
Pair Bulk IN Endpoints
Set the endpoint pairing bits (PRxIN) to “1” to enable double-buffering of the bulk IN
endpoint buffers. With double buffering enabled, the 8051 can operate on one buffer
while another is being transferred over USB.
When an endpoint is paired, the 8051 should access only the even-numbered endpoint of
the pair. The 8051 should not use the IRQ, IEN, VALID bits or the buffer associated with
the odd numbered endpoint.
EZ-USB TRM v1.9
Chapter 12. EZ-USB Registers
Page 12-43