MPC8280 datasheet(469/1386 Pages) FREESCALE

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Memory Controller

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

Freescale Semiconductor

11-49

11.4.12.1 SDRAM Configuration Example (Page-Based Interleaving)

Consider the following SDRAM organization:

•

64-bit port size, organized as eight 64-Mbit devices, each organized as 8M x 8bits.

•

Each device has 4 internal banks, 12 rows, and 9 columns

For page-based interleaving, the address bus should be partitioned as shown in Table 11-22.

The following parameters can be extracted:

•

PSDMR[PBI] = 1—Page-based interleaving

•ORx[BPD] = 01—Four internal banks

•ORx[ROWST] = 0110—Row starts at A[6]

•ORx[NUMR] = 011—Twelve row lines

Now, from the SDRAM device point of view, during an ACTIVATE command, its address port should look

like Table 11-23.

Table 11-20 on page 11-38 indicates that to multiplex A[6–17] over A[17–28], PSDMR[SDAM] must be

011 and, because the internal bank selects are multiplexed over A[15–16], PSDMR[BSMA] must be 010

(only the lower two bank select lines are used).

When using bank-based interleaving, the internal bank-select signals that are multiplexed over the address

lines should be adjacent to the row address during the ACTIVATE command (refer to Table 11-23). So, the

value of PSDMR[BSMA] is selected according to the combination of PSDMR[SDAM], ORx[ROWST],

and ORx[NUMR]. Otherwise, the output of the BNKSEL pins could be incorrect even if the device is

connected to the BNKSEL pins. To ensure proper connection, note that BNKSEL0 is msb and BNKSEL2

is lsb as stated in Table 6-1.

When using page-based interleaving, the internal bank-select signals that are mutilplexed over the address

lines are determined only by PSDMR[BSMA] during the ACTIVATE command. The output of the BNKSEL

pins are not affected by the PSDMR[BSMA] value.

During a READ/WRITE command, the address port should look like Table 11-24.

Table 11-22. 60x Address Bus Partition

A[0–5]

A[6–17]

A[18–19]

A[20–28]

A[29–31]

msb of start address

Row

Bank select

Column

lsb

Table 11-23. SDRAM Device Address Port during ACTIVATE Command

“A[0–14]”

A[15–16]

A[17–28]

A[29–31]

—

Internal bank select (A[18–19])

Row (A[6–17])

n.c.

Table 11-24. SDRAM Device Address Port during READ/WRITE Command

“A[0–14]”

A[15–16]

A[17]

A[18]

A[19]

A[20–28]

A[29–31]

—

Internal bank select

Don’t care

Column

n.c.

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