DS1925 datasheet(9/46 Pages) MAXIM

9 / 46 page

Memory

Figure 5 shows the DS1925’s memory map. The 512

bytes of general-purpose nonvolatile memory is located

in pages 0 to 15. The general-purpose is write once with

an optional reset using the XPC Clear Memory command.

The various registers to set up and control the device fill

pages 16 and 17, called register pages 1 and 2 (details in

Figure 6). The data-log logging memory starts at address

1000h (page 122) and extends over 3920 pages. The

memory pages 18 to 127 are reserved for future exten-

sions. The scratchpad is an additional page that acts as a

buffer when writing to the SRAM memory or the register

page. The data memory can be written at any time. See

the Security by Password section for ways to protect

the memory. The access type for the register pages is

programmed for a mission. Figure 6 shows the details.

The data-log memory is read-only for the user. It is writ-

ten solely under supervision of the on-chip control logic.

See the Address Registers and Transfer Status section

for details.

Several commands provide a repeating result byte as

described in Table 1.

Figure 5. Memory Map

Table 1. Repeating Byte Commands

DS1925

iButton High-Capacity Temperature Logger

with 122KB Data-Log Memory

www.maximintegrated.com

Maxim Integrated │ 9

REPEAT BYTE

DESCRIPTION

FFh

Operation not complete

AAh

(or 55h) Operation success

22h

Unable to complete the operation due to mission is in progress

44h

Error writing memory: Possibly writing memory that needs to be cleared

77h

Invalid parameter in operation

33h

Invalid authorization sequence: usually indicates TA1/TA2/ES is not correct in a copy operation

11h

Invalid password

00h

Unable to complete operation, requires XPC clear memory (log) sequence required

32-BYTE INTERMEDIATE STORAGE SCRATCHPAD

ADDRESS

00000h–0001Fh

32-BYTE GENERAL-PURPOSE NV MEMORY (R/W)

PAGE 0

00020h–001FFh

GENERAL-PURPOSE NV MEMORY (R/W)

PAGES 1 TO 15

00200h–0021Fh

32-BYTE REGISTER PAGE 1

PAGE 16

00220h–0023Fh

32-BYTE REGISTER PAGE 2

PAGE 17

00240h–0025Fh

(RESERVED FOR FUTURE EXTENSIONS)

PAGE 18

00260h- 0027Fh

32-BYTE MISSION BACKUP REGISTER PAGE 1 (READ-ONLY)

PAGE 19

00280h- 0029Fh

32-BYTE MISSION BACKUP REGISER PAGE 2 (READ-ONLY)

PAGE 20

002A0h- 00FFFh

(RESERVED FOR FUTURE EXTENSIONS)

PAGES 21 TO 127

01000h- 1F9FFh

DATA-LOG MEMORY (READ-ONLY)

PAGES 128 TO 4047

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