SEC Controller
MSC8144E Reference Manual, Rev. 3
Freescale Semiconductor
26-15
The arbiter uses the channel EU priority count field for each of these channels to keep track of the
arbitration losses. When the channel has lost the arbitration (that is, is not granted access) for the
specified EU the number of times specified in its count field, then that channel becomes the
second highest priority when the requested EU becomes available. Channel 1 always has the
highest priority, but it cannot make back-to-back requests, so the second highest priority channel
is serviced upon completion of the current channel 1 operation.
Note:
Access to the system bus uses the same type of arbitration as the EU access. The
arbitration methods do not have to be configured as the same. That is, you can use
weighted priority for one and round-robin priority for the other.
26.2.2.2 Round-Robin Arbitration
In round-robin arbitration, requesting channels are granted access in rotating numerical order: 1,
2, 3, 4, 1, 2, 3, 4, and so on.
26.2.3 Bus Transfers
The controller is involved in transfers on the system bus and the internal bus. The system bus
actually refers to two buses:
Slave for operating SEC as a slave
Master for transactions with SEC as the master
The internal bus is 64 bits wide, with the controller block as the sole master. All accesses to SEC
from the system bus go through the controller. The controller also directs transfers over the
internal bus.
For core processor-controlled access, the core processor uses the external bus to access the
controller as a slave, and the controller relays the read or write accesses to the proper block over
the internal bus. When a write command is received from the system bus, the controller takes the
data and sends it to the internal location indicated by the address. For a read, the controller goes
to the internal location, fetches the requested data from the specified address, and returns it over
the system bus.
For channel-controlled access, the channels make requests to the controller to perform data
transfers. The channel specifies data lengths and addresses for the internal and system buses.
Multiple channels may request use of the controller at the same time, so the controller performs
arbitration to choose a channel. The controller then services the request and performs the required
transfer. Most transfers involve not only the internal bus, but also the system bus with the
controller as bus master. Here are examples of the various types of transfers:
Obtaining a descriptor:
— channel makes request, arbitrates for attention from controller
— controller arbitrates for use of the system bus and performs read from external memory
Summary of Contents for MSC8144E
Page 1: ...MSC8144E Reference Manual Quad Core Media Signal Processor MSC8144ERM Rev 3 July 2009 ...
Page 48: ...MSC8144E Reference Manual Rev 3 xlviii Freescale Semiconductor ...
Page 86: ...MSC8144E Reference Manual Rev 3 1 38 Freescale Semiconductor Overview ...
Page 168: ...MSC8144E Reference Manual Rev 3 3 60 Freescale Semiconductor External Signals ...
Page 242: ...MSC8144E Reference Manual Rev 3 5 26 Freescale Semiconductor Reset ...
Page 314: ...MSC8144E Reference Manual Rev 3 8 24 Freescale Semiconductor General Configuration Registers ...
Page 414: ...MSC8144E Reference Manual Rev 3 10 14 Freescale Semiconductor MSC8144E SC3400 DSP Subsystem ...
Page 452: ...MSC8144E Reference Manual Rev 3 11 38 Freescale Semiconductor Internal Memory Subsystem ...
Page 520: ...MSC8144E Reference Manual Rev 3 12 68 Freescale Semiconductor DDR SDRAM Memory Controller ...
Page 1070: ...MSC8144E Reference Manual Rev 3 21 28 Freescale Semiconductor Timers ...