MPC8280 datasheet(495/1386 Pages) FREESCALE

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Memory Controller

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

Freescale Semiconductor

11-75

Additional information about some of the RAM word fields is provided in the following sections.

11.6.4.1.1

Chip-Select Signals (C

xTx)

If BRx[MS] of the accessed bank selects a UPM on the currently requested cycle the UPM manipulates

the CS signal for that bank with timing as specified in the UPM RAM word. The selected UPM affects

only assertion and negation of the appropriate CS signal. The state of the selected CSx signal of the

corresponding bank depends on the value of each CSTn bit.

Next address. Determines when the address is incremented during a burst access.

0 The address increment function is disabled

1 The address is incremented in the next cycle. In conjunction with the BR

x[PS], the increment

value of A[27–31] and/or BADDR[27–31] at the rising edge of T1 is as follows

If the accessed bank has a 64-bit port size, the value is incremented by 8.

If the accessed bank has a 32-bit port size, the value is incremented by 4.

If the accessed bank has a 16-bit port size, the value is incremented by 2.

If the accessed bank has an 8-bit port size, the value is incremented by 1.

Note: The value of NA is relevant only when the UPM serves a burst-read or burst-write request. NA

is reserved under other patterns.

UTA

UPM transfer acknowledge. Indicates assertion of PSDVAL, sampled by the bus interface in the

current cycle.

0 PSDVAL is not asserted in the current cycle.

1 PSDVAL is asserted in the current cycle.

TODT

Turn-on disable timer. The disable timer associated with each UPM allows a minimum time to be

guaranteed between two successive accesses to the same memory bank. This feature is critical

when DRAM requires a RAS precharge time. TODT, turns the timer on to prevent another UPM

access to the same bank until the timer expires.The disable timer period is determined in

xMR[DSx]. The disable timer does not affect memory accesses to different banks.

0 The disable timer is turned off.

1 The disable timer for the current bank is activated preventing a new access to the same bank

(when controlled by the UPMs) until the disable timer expires. For example, precharge time.

Note: TODT must be set together with LAST. Otherwise it is ignored.

LAST

Last. If this bit is set, it is the last RAM word in the program. When the LAST bit is read in a RAM

word, the current UPM pattern terminates and the highest priority pending UPM request (if any) is

serviced immediately in the external memory transactions. If the disable timer is activated and the

next access is top the same bank, the execution of the next UPM pattern is held off for the number

of clock cycles specified in MxMR[DSx].

0 The UPM continues executing RAM words.

1 The service to the UPM request is done.

Table 11-36. RAM Word Bit Settings (continued)

Bit

Name

Description

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