MPC8540 datasheet(578/1302 Pages) FREESCALE

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MPC8540 PowerQUICC III Integrated Host Processor Reference Manual, Rev. 1

13-74

Freescale Semiconductor

Local Bus Controller

loop end word. Loops can be executed sequentially but cannot be nested. Also, special care must

be taken if LAST and LOOP must not be set together.

13.4.4.4.6 Repeat Execution of Current RAM Word (REDO)

The REDO function is useful for wait-state insertion in a long UPM routine that would otherwise

need too many RAM words. Setting the REDO bits of the RAM word to a nonzero value causes

the UPM to re-execute the current RAM word up to three more times, as defined in the REDO field

of the current RAM word.

Special care must be taken in the following cases:

•

When UTA and REDO are set together, TA is asserted the number of times specified by the

REDO function.

•

When NA and REDO are set together, the address is incremented the number of times

specified by the REDO function.

•

When LOOP and REDO are set together, the loop mechanism works as usual and the line

is repeated according to the REDO function.

•

LAST and REDO must not be set together.

•

REDO should not be used within the exception routine.

13.4.4.4.7 Address Multiplexing (AMX)

The address lines can be controlled by the pattern the user provides in the UPM. The address

multiplex bits can choose between driving the transaction address, driving it according to the

multiplexing specified by the MxMR[AM] field, or driving the MAR contents on the address

signals. In all cases, LA[27:31] of the LBC are driven by the five lsbs of the address selected by

AMX, regardless of whether the NA bit of the RAM word is used to increment the current address.

The effect of NA = 1 is visible only when AMX = 00 chooses the column address.

Table 13-32 shows how MxMR[AM] settings affect address multiplexing when the RAM word

AMX = 10. The 16 msbs of the LAD[0:31] bus during an address phase are driven with zero in

the AMX = 10 case.

Table 13-31. MxMR Loop Field Use

Request Serviced

Loop Field

Read single-beat cycle

RLF

Read burst cycle

RLF

Write single-beat cycle

WLF

Write burst cycle

WLF

Refresh timer expired

TLF

RUN command

RLF

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