TSB43AA82A Datasheet, PDF (91/147 Pages) Texas Instruments – 1394 Integrated PHY and Link-Layer Controller for SBP-2 Products and DPP Products

7.3.2.3 Link Abort and DEAD State
The host can change the command agent to the DEAD state. For example, when a task is aborted for some reason,
the command agent changes to a DEAD state. For more details, please refer to the SBP-2 standard. Setting Dead(n)
in the agent status register (5Ch) changes the state of the command agent into a DEAD state. Read requests
addressed to agent state from the initiator are automatically responded to with a DEAD state.
Quadlet write requests to the AGENT_RESET register (see Section 7.1.1) by the initiator allow the command agent
to recover from a DEAD state. This resets the command agent and changes the state back to IDLE.
7.3.2.4 SBP-2/Doorbell
The transaction for a write to the DOORBELL register (see Section 7.1.1) is explained below:
The TSB43AA82A agent is in suspended state when the ORB address shown in next_ORB or ORB_offset
shows dummy ORB (FFFF FFFF FFFF FFFFh). The initiator activates the command agent by transmitting
a quadlet write request to the DOORBELL register (see Section 7.1.1). When the quadlet write request is
received at the DOORBELL register by the command agent, DrBell(n) in the agent status register (5Ch) is
set to 1. When necessary, the host sets DrBClr(n) to 1 to clear DrBell(n). Figure 7−6 shows a typical
suspended and doorbell request.
NOTE: The host cannot activate a suspended agent.
Target
Initiator
AgntWr_Int
DrBllx
COAF_Agent and CTQ
Quadlet Write Request
DOORBELL Register
Notify Command ORB has
Effective Next ORB Address.
Command Agent
No Packet in CRF
CAgXRdy = 1 (When
Next ORB Exists)
CRF
COREnd_Int
Clear DOORBELL (See Note 1)
Host Reads Out CRF
Block Read Request
Dummy ORB Offset Address
Block Read Response
Dummy ORB
Block Read Request
Command Block ORB Offset Address
Command ORB
Dummy ORB Response.
Contents of Packet Is Linked
Command ORB.
Command ORB Response.
Contents of Packet Is Linked
Command ORB.
Status Block
NOTE 1: The DOORBELL register can be cleared by setting DrBClr(n).
Figure 7−6. SUSPENDED and DOORBELL Request by Dummy ORB
7−9