ADUC812(1999) 查看數據表（PDF） - Analog Devices

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ADUC812
(Rev.:1999)

MicroConverter™, Multichannel 12-Bit ADC with Embedded FLASH MCU

Analog Devices 

ADuC812

A block diagram of the SFR registered interface to the User

Flash/EE Memory array is shown in Figure 12.

Flash/EE Memory Write and Erase Times

The typical program/erase times for the User Flash/EE Memory

are:

FUNCTION:

HOLDS THE 8-BIT PAGE

ADDRESS POINTER

FUNCTION:

HOLDS THE 4-BYTE

PAGE WORD

9FH BYTE 1 BYTE 2 BYTE 3 BYTE 4

Erase Full Array (640 Bytes) – 20 ms

Erase Single Page (4 Bytes) – 20 ms

Program Page (4 Bytes)

– 250 µs

Read Page (4 Bytes)

– Within Single Instruction Cycle

EADRL

EDATA1 (BYTE 1)

EDATA2 (BYTE 2)

EDATA3 (BYTE 3)

EDATA4 (BYTE 4)

00H BYTE 1 BYTE 2 BYTE 3 BYTE 4

ECON COMMAND

INTERPRETER LOGIC

FUNCTION:

HOLDS COMMAND WORD

ECON

FUNCTION:

INTERPRETS THE FLASH

COMMAND WORD

Figure 12. User Flash/EE Memory Control and

Configuration

ECON—Flash/EE Memory Control SFR

This SFR acts as a command interpreter and may be written

with one of five command modes to enable various read, pro-

gram and erase cycles as detailed in Table VI:

Table VI. ECON–Flash/EE Memory Control Register

Command Modes

Command Byte Command Mode

01H

02H

03H

04H

05H

06H

07H to FFH

READ COMMAND

Results in four bytes being read into

EDATA 1–4 from memory page location

contained in EADRL .

WRITE COMMAND

Results in four bytes (EDATA 1–4) being

written to memory page location in EADRL.

This write command assumes the de-

signated “write” page has been pre-erased.

RESERVED COMMAND

“DO NOT USE”

VERIFY COMMAND

Allows the user to verify if data in EDATA

1–4 is contained in page location designated

by EADRL. A subsequent read of the

ECON SFR will result in a “zero” being

read if the verification is valid, a nonzero

value will be read to indicate an invalid

verification.

ERASE COMMAND

Results in an erase of the 4-byte page

designated in EADRL.

ERASE-ALL COMMAND

Results in erase of the full user memory

160-page (640 bytes) array.

RESERVED COMMANDS

Commands reserved for future use.

Using the Flash/EE Memory Interface

As with all Flash/EE memory architectures, the array can be pro-

grammed in system at a byte level, although it must be erased

first; the erasure being performed in page blocks (4-byte pages

in this case).

A typical access to the Flash/EE array will involve setting up the

page address to be accessed in the EADRL SFR, configuring the

EDATA1-4 with data to be programmed to the array (the

EDATA SFRs will not be written for read accesses) and finally

writing the ECON command word which initiates one of the

five modes shown in Table VI.

It should be noted that a given mode of operation is initiated as

soon as the command word is written to the ECON SFR. At

this time the core microcontroller operation on the ADuC812

is idled until the requested Program/Read or Erase mode is

completed.

In practice, this means that even though the Flash/EE memory

mode of operation is typically initiated with a 2 machine cycle

MOV instruction (to write to the ECON SFR), the next

instruction will not be executed until the Flash/EE operation

is complete (250 µs or 20 ms later). This means that the core

will not respond to Interrupt requests until the Flash/EE

operation is complete, although the core peripheral functions

like Counter/Timers will continue to count and time as configured

throughout this pseudo-idle period.

ERASE-ALL

Although the 640-byte User Flash/EE array is shipped from the

factory pre-erased, i.e., Byte locations set to FFH, it is nonethe-

less good programming practice to include an erase-all routine

as part of any configuration/setup code running on the ADuC812.

An “ERASE-ALL” command consists of writing “06H” to the

ECON SFR, which initiates an erase of all 640 byte locations in

the Flash/EE array. This command coded in 8051 assembly

would appear as:

MOV ECON, #06H

; Erase all Command

; 20 ms Duration

PROGRAM A BYTE

In general terms, a byte in the Flash/EE array can only be

programmed if it has previously been erased. To be more spe-

cific, a byte can only be programmed if it already holds the value

FFH. Because of the Flash/EE architecture this erasure must

happen at a page level, therefore a minimum of four bytes (1 page)

will be erased when an erase command is initiated.

A more specific example of the Program-Byte process is shown

graphically in Figure 13. In this example the user will write F3H

into the second byte on Page 03H of the User Flash/EE Memory

space.

However, Page 03H already contains four bytes of valid data,

and as the user is only required to modify one of these bytes, the

full page must be first read so that this page can then be erased

without the existing data being lost.

–14–

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