CD2401 Intel, CD2401 Datasheet - Page 53

• Manufacturer Part Number: CD2401
• Description: Multi-protocol Communications Controller
• Manufacturer: Intel

Datasheet
Example 2
Receive a frame on channel 0, which consists of three buffers chained together. The frame is
240-bytes long, and the maximum buffer size is 100.
10. After the CD2401 has received the second link into buffer A, it sets EOB bit and clears the
12. By this time, the host has set up a new buffer for buffer B.
13. The CD2401 receives data into buffer B in the same manner previously explained.
14. In this example, the third link does not fill the buffer. Thus, when the end-of-frame delimiter is
15. Next, the CD2401 sets the EOB and EOF bits to show that the buffer is complete, and that this
16. The CD2401 optionally interrupts the host with EOF and EOB set (RISRh[6:5]) to indicate
11. The CD2401 optionally interrupts the host with EOF clear and EOB set (RISRh[6:5]) to
1. The host checks the Nrbuf bit (DMABSTS[1]) for channel 0 to determine which buffer is next.
2. The host sets up the starting address, BRBADR. Buffer size is set to 100 in this example. Thus,
3. The host then sets the 2401own bit to relinquish ownership to the CD2401.
4. The host should know the amount of time it takes to receive 100 bytes, because this is the
5. Suppose that the CD2401 starts receiving data into buffer B of channel 0. When this is started,
6. After the CD2401 has received the first link of the frame into buffer B, it sets the EOB and
7. The CD2401 optionally interrupts the host with EOF clear and EOB set (RISRh[6:5]) to
8. The CD2401 now sees from the ARBSTS register that it has ownership of buffer A for
9. As the frame continues to be received, the data goes into buffer A. This is the second link that
In this example, Nrbuf set to ‘1’ indicates buffer B is used next.
the host sets BRBCNT to ‘100’.
minimum time the host has to set up the next buffer link. If the host fails to do this in time,
there is a receiver overrun, and the received frame is lost.
the Nrbuf bit is cleared to ‘0’ by the CD2401 to help the host keep track of which buffer is
next. (During or prior to this, the host has made buffer A ready.)
SOB bits and clears the EOF bit. This indicates that the first link in a chain has been received.
Also, the CD2401 clears the 2401own bit and returns ownership of the buffer to the host.
For the first received link, the received byte count (BRBCNT) remains unchanged at 100 since
the received data filled the buffer.
indicate that the received buffer is complete, and that there was chaining.
transmission of the next link.
is 100 bytes long. During this time, the host must set up a new buffer B for the third and final
link.
2401own bit (ARBSTS[0]). This returns ownership of the buffer to the host.
As with the first link, the received byte count (ARBCNT) remains unchanged at 100 since the
received data filled the buffer.
indicate that the received buffer is complete, and there was chaining.
detected by the CD2401, the value of 40 (for 40 received bytes) is written into the received
byte count (BRBCNT).
is the last link in the chain.
that the received frame is complete, and this was the last link in the chain.
Multi-Protocol Communications Controller — CD2401
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