In addition to the 32-bit input and output ports discussed in the previous section, the Diamond 570T CPU core has a 32-bit input-queue interface and a 32-bit output queue interface. These queue interfaces, respectively, connect directly to the head or tail of a FIFO memory. Each queue interface has a pair of hardware handshaking wires that automatically sequence the flow of data between the attached FIFO memory and the processor. The input-queue handshake signals are called PopReq (Pop Request) and Empty. The output-queue handshake signals are called PushReq (Push Request) and Full.
Table 10.7 lists the instructions added to the Diamond 570T CPU to manage the input and output queue interfaces.