MEC1632 datasheet(155/636 Pages) MICROCHIP

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DS00001592B-page 155

MEC1632

Each window into the EC memory can be as large as 32K bytes. The Embedded Memory Interface uses the EC’s DCCM

Direct Memory Interface (DMI) in order to access the memory. Figure 8-4, "Embedded Memory Region Address Control"

shows the relationship between one of the regions in the Embedded Memory Interface and the DCCM DMI:

8.4.2

EMBEDDED MEMORY INTERFACE USAGE

The Embedded Memory Interface provides a generic facility for communication between the Host and the EC and can

be used for many functions. Some examples are:

• Virtual registers. A block of read-only memory locations in the DCCM can be used to implement a set of virtual

registers. The EC can update these locations with that the Host can later read.

• Program downloading. Because the Instruction Closely Coupled Memory is implemented in the same SRAM as

the DCCM, the Embedded Memory Interface can be used by the Host to download new program segments for the

EC. The Read/Write window would be configured by the Host to point to the beginning of the loadable program

region, which could then be loaded by the Host.

• Data exchange. The Read/Write portion of the memory window can be used to contain a communication packet.

The Host, by default, “owns” the packet, and can write it at any time. When the Host wishes to communicate with

the EC, it sends the EC a command, through the Host-to-EC message facility, to read the packet and perform

some operations as a result. When it is completed processing the packet, the EC can inform the Host, either

through a message in the EC-to-Host channel or by triggering an event such as an SMI directly. If return results

are required, the EC can write the results into the Read/Write region, which the Host can read directly when it is

informed that the EC has completed processing. Depending on the command, the operations could entail update

of virtual registers in the DCCM, reads of any register in the EC address space, or writes of any register in the EC

address space. Because there are two regions that are defined by the base registers, the memory used for the

communication packet does not have to be contiguous with a set of virtual registers.

FIGURE 8-4:

EMBEDDED MEMORY REGION ADDRESS CONTROL

EC Data

EC Address

Write Limit

Read Limit

Memory Base

dmi_rdata

dmi_wdata

dmi_addr

DCCM

dmi_we

dmi_req

Logic

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