MSM548262-60JS datasheet(33/37 Pages) OKI

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MSM548262

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DATA TRANSFER OPERATIONS

The MSM548262 features two types of bidirectional data transfer capability between RAM and

SAM.

1) Conventional (non split) transfer: 512 words by 8 bits of data can be loaded from RAM to SAM

(Read transfer), or from SAM to RAM (Write transfer).

2) Split transfer: 256 words by 8 bits of data can be loaded from the lower/upper half of the RAM

to the lower/upper half of the SAM (Split read transfer), or from the lower/upper half of SAM

to the lower/upper half of RAM (Split write transfer).

The conventional transfer and split transfer modes are controlled by the DSF input signal.

Data transfer are invoked by holding the TRG signal "low" at the falling edge of RAS.

The MSM548262 supports 4 types of transfer operations: Read transfer, Split read transfer, Write

transfer and Split write transfer as shown in the truth table. The type of transfer operation is

determined by the state of CAS, WE and DSF latched at the falling edge of RAS. During

conventional transfer operations, the SAM port is switched from input to output mode (Read

transfer), or output to input mode (Write transfer). It remains unchanged during split transfer

operation (Split read transfer or Split write transfer).

Both RAM and SAM are divided by the most significant row address (AX8), as shown in Figure

1. Therefore, no data transfer between AX8 = 0 side RAM and AX8 = 1 side RAM can be provided

through the SAM. Care must be taken if the split read transfer on AX8 = 1 side (or AX8 = 0 side)

is provided after the read transfer or the split read transfer, is provided on AX8 = 0 side (or AX8

= 1 side).

Figure 1. RAM and SAM Configuration

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Memory

Array

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Memory

Array

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Memory

Array

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Memory

Array

AX8 = 0

AX8 = 1

SAM I/O Buffer

SDQ1 - 8

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