STLC1502 datasheet(12/81 Pages) STMICROELECTRONICS

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STLC1502

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6.2 ESM interface

•

The ESM (External Static Memory) interface is used to access static RAMs or Flash devices. It pro-

vides 3 chip select signals and gives external access to 21 address bits, so that the memory space

accessible through each chip select is 4 Mbytes.

•

The data bus on ESM external interface is 32bits wide, with the additional ability to perform 16 and 8

bits accesses. Little endian byte ordering is used. The data bus and address bus pins are shared with

the DRAM driver, using EBI interface.

•

Programmable per chip-select wait-states from 0 to 15 internal clock cycles are available.

•

At reset, every CS space has 15 wait states. The actual value is contained in the downloaded code.

•

The external memory spaces are mapped by the ESM interface as reported in Figure 4.

•

There are 3 addressable memory spaces 0x00400000 byte long each.

Figure 4: ESM memory map

Following is the list of the available external signals that implement SRAM or FLASH read and write cycles. Data

and address buses are not shown as they are shared with the DRAM EBI interface.

NAME

Signal type

Description

ESM_CS(2:0)

OUT

Chip Select. Asserted when the

ESM decodes the proper address

space in order to select the right

external device

OUT

Output Enable. Asserted during a

read cycle (shared with EDM)

External

ESM

04000000

ESM_CS1

ESM_CS0

ESM_CS2

Reserved

04000000

043FFFFF

047FFFFF

04800000

04BFFFFF

07FFFFFF

04400000

04C00000

Memories

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