TABLE OF CONTENTS When an N_Port or F_Port transmits a Data Frame or Link Control Frame, a number of responses can be returned. These include the R_RDY response, for link level buffer-to-buffer flow control, and the Link control Frames, which can be returned for Data Frames and sometimes for other Link Control Frames as well. This section describes in more detail the responses to Frame transmission and the detailed handling of the various Link Control Frames.
As described in the R_RDY section, on page 95, the R_RDY Primitive Signal is transmitted in response to a Frame when enough processing has been done at the receiver that another Frame can be accepted. R_RDY is used for buffer-to-buffer flow control between two attached Ports for Class 2, Class 3, and Class 1 connect-request Data Frames and Link Control Frames. For the Class 1 connect-request, R_RDY is only used for flow control and does not indicate whether the Connection has been made. When an R_RDY is received, it indicates that an interface buffer and associated resources are available for receiving one more Frame. There may be multiple interface buffers supported, and the number of buffers is specified during Fabric Login.
The ACK Frame is used for end-to-end flow control in Class 1 and Class 2 Sequences, as described in Chapter 15. Return of an ACK Frame indicates that one or more Data Frames were received by the destination N_Port and transferred out of the...
