M58LT128GS datasheet(37/98 Pages) STMICROELECTRONICS

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M58LT128GST, M58LT128GSB

6 Configuration Register

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6.7

Valid Clock Edge Bit (CR6)

The Valid Clock Edge bit, CR6, is used to configure the active edge of the Clock, K, during

synchronous read operations. When the Valid Clock Edge bit is Low (set to ’0’) the falling edge

of the Clock is the active edge. When the Valid Clock Edge bit is High (set to ’1’) the rising edge

of the Clock is the active edge.

6.8

Wrap Burst Bit (CR3)

The Wrap Burst bit, CR3, is used to select between wrap and no wrap. Synchronous burst

reads can be confined inside the 4, 8 or 16 Word boundary (wrap) or overcome the boundary

(no wrap).

When the Wrap Burst bit is Low (set to ‘0’) the burst read wraps. When it is High (set to ‘1’) the

burst read does not wrap.

6.9

Burst length Bits (CR2-CR0)

The Burst Length bits are used to set the number of Words to be output during a Synchronous

Burst Read operation as result of a single address latch cycle.

They can be set for 4 Words, 8 Words, 16 Words or continuous burst, where all the Words are

read sequentially. In continuous burst mode the burst sequence can cross bank boundaries.

In continuous burst mode, in 4, 8 or 16 Words no-wrap, depending on the starting address, the

device asserts the WAIT signal to indicate that a delay is necessary before the data is output.

If the starting address is aligned to an 8 Word boundary no WAIT states are needed and the

WAIT output is not asserted.

If the starting address is not aligned to the 8 Word boundary, WAIT will be asserted when the

burst sequence crosses the first 16 Word boundary to indicate that the device needs an internal

delay to read the successive Words in the array.

In the worst case, the number of WAIT states is one clock cycle less than the latency setting.

The exact number is reported in Table 12: Wait at the Boundary.

WAIT will be asserted only once during a continuous burst access. See also Table 11: Burst

Type Definition.

CR14, CR5 and CR4 are reserved for future use.

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