MPC8280 datasheet(443/1386 Pages) FREESCALE

443 / 1386 page

Memory Controller

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

Freescale Semiconductor

11-23

EAMUX

External address multiplexing enable/disable.

0 No external address multiplexing. Fastest timing.

1 The memory controller asserts SDAMUX for an extra cycle before issuing an ACTIVATE

command to the SDRAM. This is useful when external address multiplexing can cause a

delay on the address lines. Note that if this bit is set, ACTTORW should be a minimum of 2.

In 60x-compatible mode, external address multiplexing is placed on the address lines. If the

additional delay of the multiplexing endangers the device setup time, EAMUX should be set.

Setting this bit causes the memory controller to add another cycle for each address phase.

Note that EAMUX can also be set in any case of delays on the address lines, such as address

buffers. See Section 11.4.6.7, “External Address Multiplexing Signal.”

BUFCMD

If external buffers are placed on the control lines going to both the SDRAM and address lines,

setting BUFCMD causes all SDRAM control lines except CS to be asserted for two cycles,

instead of one. See Section 11.4.6.8, “External Address and Command Buffers (BUFCMD).”

0 Normal timing for the control lines

1 All control lines except CS are asserted for two cycles

In 60x-compatible mode, external buffers may be placed on the command strobes, except CS,

as well as the address lines. If the additional delay of the buffers endangers the device setup

time, BUFCMD should be set, which causes the memory controller to add a cycle for each

SDRAM command.

30–31

CAS latency. Defines the timing for first read data after SDRAM samples a column address. See

Section 11.4.6.3, “Column Address to First Data Out—CAS Latency.”

00 Reserved

01 1

10 2

11 3

Table 11-8. PSDMR Field Descriptions (continued)

Bits

Name

Description

MPC8280 데이터시트(PDF) 443 Page - Freescale Semiconductor, Inc