Memory Controller
MPC885 PowerQUICC Family Reference Manual, Rev. 2
Freescale Semiconductor
15-33
15.6.1
Requests
An internal or external master’s request for a memory access initiates one of the following patterns:
•
Read single-beat pattern (RSS)
•
Read burst cycle pattern (RBS)
•
Write single-beat pattern (WSS)
•
Write burst cycle pattern (WBS)
These patterns are described in
Section 15.6.1.1, “Internal/External Memory Access Requests.”
A UPM periodic timer request pattern initiates a periodic timer pattern (PTS), as described in
Section 15.6.1.2, “UPM Periodic Timer Requests.”
An exception (reset or machine check triggered by the assertion of TEA) occurring while another UPM
pattern is running initiates an exception condition pattern (EXS).
A special pattern in the RAM array is associated with each of these cycle types.
Figure 15-32
shows the
start addresses of these patterns in the UPM RAM, according to cycle type. MCR-initiated
RUN
commands, however, can initiate patterns starting at any of the 64 UPM RAM words.
Figure 15-32. RAM Array Indexing
15.6.1.1
Internal/External Memory Access Requests
When an internal master requests a new access to external memory, the address and type of transfer are
compared to each valid bank defined in BRx. The value in BRx[MS] selects the UPM to handle the
memory access. The user must ensure that the UPM is appropriately initialized before a request.
External memory access requests are single-beat and burst reads and writes. A single-beat transfer
transfers one operand consisting of a single byte, half word, or word. A burst transfer transfers four words.
A single-beat cycle starts with one transfer start and ends with one transfer acknowledge. For 32-bit
accesses, the burst cycle starts with one transfer start but ends after four transfer acknowledges. A 16-bit
bus requires 8 transfer acknowledges; an 8-bit bus requires 16.
Write Single-Beat Request
Read Burst Request
Read Single-Beat Request
Write Burst Request
RAM Array
Periodic Timer Request
Exception Condition Request
RSS
RBS
WSS
WBS
PTS
EXS
64 RAM
Words
Array Index
Generator
0x00
0x08
0x20
0x18
0x30
0x3C
Summary of Contents for PowerQUICC MPC870
Page 98: ...MPC885 PowerQUICC Family Reference Manual Rev 2 I 4 Freescale Semiconductor ...
Page 118: ...MPC885 Overview MPC885 PowerQUICC Family Reference Manual Rev 2 1 20 Freescale Semiconductor ...
Page 158: ...The MPC8xx Core MPC885 PowerQUICC Family Reference Manual Rev 2 3 18 Freescale Semiconductor ...
Page 288: ...MPC885 PowerQUICC Family Reference Manual Rev 2 III 4 Freescale Semiconductor ...
Page 554: ...MPC885 PowerQUICC Family Reference Manual Rev 2 V 6 Freescale Semiconductor ...
Page 1090: ...UTOPIA Interface MPC885 PowerQUICC Family Reference Manual Rev 2 43 8 Freescale Semiconductor ...
Page 1312: ...Byte Ordering MPC885 PowerQUICC Family Reference Manual Rev 2 A 8 Freescale Semiconductor ...
Page 1336: ...MPC885 PowerQUICC Family Reference Manual Rev 2 D 16 Freescale Semiconductor ...
Page 1358: ...MPC885 PowerQUICC Family Reference Manual Rev 2 D 38 Freescale Semiconductor ...
Page 1370: ...MPC880 MPC885 PowerQUICC Family Reference Manual Rev 2 E 4 Freescale Semiconductor ...
Page 1386: ...Revision History MPC885 PowerQUICC Family Reference Manual Rev 2 I 2 Freescale Semiconductor ...