cxd3220r Sony Electronics, cxd3220r Datasheet - Page 25

• Manufacturer Part Number: cxd3220r
• Description: Ieee1394 Link/transaction Layer Controller Lsi For Sbp-2
• Manufacturer: Sony Electronics

The number of quadlets that can be stored in the ATF can be found from the value of the Async Status register
bits [23:19]. The following six states can be found, so a judgment must be made as to whether write is possible
from the number of quadlets in the packet being sent from the external CPU.
6-3. Asynchronous Packet Transmission
Packet data is written from the external CPU to the ATF inside the CXD3220R in order to transmit an
Asynchronous packet. At this time the first quadlet of the packet only is written in the CFR ATFWrite (first
quadlet of the packet) register (70h). The second through the next to the last quadlets are written in the CFR
ATFWrite/ARFRead registers (74h). Then the last quadlet is written in the CFR ATFWrite (confirm write)
register (7Ch) and the packet is stored in the ATF.
However, if the ATF is full, write will not actually be performed even when write is executed.
Once the bus is enabled, transmit takes place automatically.
The procedure for transmitting a Quadlet Write request packet is given here as an example.
(for 8-bit data interface)
(1) Confirming that the ATF is not full
The CFR Async Status register (1Ch to 1Fh) is read to confirm that the 23th bit (AtfFull bit) is low. If it is high it
means that there are some unsent packets stored and it waits until they are transmitted.
ADDRESS
AtfFull = High: Can't Write
AtfAFull = High: Only one quadlet
All bits low: 2 to 3 quadlets
Atf4Avail = High: 4 to 22 quadlets
Atf4Avail = High, AtfAEmpty = High: 4 to 23 quadlets
Atf4Avail = High, AtfEmpty = High: 4 to 24 quadlets
DATA
XCS
XRD
1Ch
xxh
This indicates that the ATF is empty.
It is "80h" when the ATF is full.
1Dh
– 25 –
28h
1Eh
xxh
1Fh
xxh
CXD3220R