Cypress EZ-USB Series 2100 Service Manual download pdf (Page 228)

EZ-USB TRM v1.9 Chapter 12. EZ-USB Registers Page 12-35

* See Table 12-5 for individual control/status register addresses.

Figure 12-28. OUT Control and Status Registers

Bit 1: OUTnBSY OUT Endpoint (1-7) Busy

The BSY bit indicates the status of the endpoint’s OUT Buffer OUTnBUF. The EZ-USB

core sets BSY=0 when the host data is available in the OUT buffer. The 8051 sets BSY=1

by loading the endpoint’s byte count register.

When BSY=1, endpoint RAM data is invalid--the endpoint buffer has been emptied by the

8051 and is waiting for new OUT data from the host, or it is the process of being loaded

over the USB. BSY=0 when the USB OUT transfer is complete and endpoint RAM data

in OUTnBUF is available for the 8051 to read. USB OUT tokens for the endpoint are

NAKd while BSY=1 (the 8051 is still reading data from the OUT endpoint).

A 1-to-0 transition of BSY (indicating that the 8051 can access the buffer) generates an

interrupt request for the OUT endpoint. After the 8051 reads the data from the OUT end-

point buffer, it loads the endpoint’s byte count register with any value to re-arm the end-

point, which automatically sets BSY=1. This enables the OUT transfer of data from the

host in response to the next OUT token. The CPU should never read endpoint data while

BSY=1.

Bit 0: OUTnSTL OUT Endpoint (1-7) Stall

The 8051 sets this bit to “1” to stall an endpoint, and to “0” to clear a stall.

When the stall bit is “1,” the EZ-USB core returns a STALL Handshake for all requests to

the endpoint. This notifies the host that something unexpected has happened.

The 8051 sets an endpoint’s stall bit under two circumstances:

1. The host sends a “Set_Feature—Endpoint Stall” request to the specific endpoint.

OUTnCS Endpoint (1-7) OUT Control and Status 7FC6-7FD2*

b7 b6 b5 b4 b3 b2 b1 b0

- - - - - - OUTnBSY OUTnSTL

R R R R R R R R/W

0 0 0 0 0 0 0 0

1 2 ... 223 224 225 226 227 228 229 230 231 232 233 ... 333 334

No comments

Cypress EZ-USB Series 2100 Service Manual Page 228