Motorola MPC8260 - Manual (Page 341)

MOTOROLA Chapter 10. Memory Controller 10-65
Part III. The Hardware Interface
Table 10-34 show the start address of each pattern.
10.6.1.1 Memory Access Requests
When an internal device requests a new access to external memory, the address of transfer
are compared to each valid bank deÞned 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.
The UPM supports two types of memory reads and writes:
¥ A single-beat transfer transfers one operand consisting of up to double word. A
single-beat cycle starts with one transfer start and ends with one transfer
acknowledge.
¥ A burst transfer transfers four double words. For 64-bit accesses, the burst cycle
starts with one transfer start but ends after four transfer acknowledges. A 32-bit
device requires 8 data acknowledges; an 8-bit device requires 32. See
Section 10.2.13, ÒPartial Data Valid Indication (PSDVAL).Ó
The MPC8260 deÞnes two additional transfer sizes: bursts of two and three doublewords.
These access are treated by the UPM as back-to-back, single-beat transfers.
10.6.1.2 UPM Refresh Timer Requests
Each UPM contains a refresh timer that can be programmed to generate refresh service
requests of a particular pattern in the RAM array. Figure 10-57 shows the hardware
associated with memory refresh timer request generation. PURT deÞnes the period for the
timers associated with UPMx on the 60x bus and LURT deÞnes it on the local bus. See
Section 10.3.8, Ò60x Bus-Assigned UPM Refresh Timer (PURT),Ó and Section 10.3.9,
ÒLocal Bus-Assigned UPM Refresh Timer (LURT).Ó
All 60x bus refreshes are done using the refresh pattern of UPMA. This means that if
refresh is required on the 60x bus, UPMA must be assigned to the 60x bus and
MxMR[RFEN] must be set. It also means that only one refresh routine should be
programmed for the 60x bus and be placed in UPMA, which serves as the 60x bus refresh
executor. If refresh is not required on the 60x bus, UPMA can be assigned to any bus.
Table 10-34. UPM Routines Start Addresses
UPM Routine Routine Start Address
Read single-beat (RSS) 0x00
Read burst (RBS) 0x08
Write single-beat (WSS) 0x18
Write burst (WBS) 0x20
Refresh timer (PTS) 0x30
Exception condition (EXS) 0x3C