Reading Nonvolatile Memory (NVM)

NVM stores system activity parameters, including a circular queue of the last six ISL utilities executed, which is useful as a diagnostic aid in the event of a system crash or failure.

NVM contains initialization information in a 92-byte block starting at decimal byte address 36. NVM stores this information as shown in figure C-2.

Figure C-2 NVM Contents

To read an NVM location, enter the ISL READNVM command and enter the hexadecimal or decimal address. The output is always in hexadecimal. In the following examples, addresses are referred to in decimal notation and the output is in hexadecimal notation.

The last boot path, starting at byte address decimal 36, contains the status of the autoboot and autosearch flags during the boot sequence.

Address decimal 68 contains the ISL revision number in ASCII.

ISL> READNVM 68



   Address 68 contains 0x32363334   *** ISL Revision 2738 ***

The TIMESTAMP is in seconds since 1/1/70.

Locations 76 through 123 contain the names of the utilities booted. They are placed into a circular queue. The pointer at location 124 (first two digits) is positioned to the last utility executed. The pointer ranges from 1-6 (decimal) or 01-06 (hexadecimal), indicating which utility (1-6 - top to bottom on figure C-2) was last executed.

   ISL> READNVM 124



     Address 124 contains 0x030600AC

The first two digits, 03, indicate that the pointer is positioned to the third utility name location (decimal address 92) in the queue.

Read location 92 to find the hexadecimal representation of the name:

   ISL> READNVM 92



      Address 92 contains 0x53544152

(53=S 54=T 41=A 52=R which spells out STAR)

Since each location is limited to four characters, additional characters are located in the next word:

   ISL> READNVM 96



     Address 96 contains 0x54202020

(54=T 20=Blank which adds the last T for start)

Table C-1 lists the ISL utility names and the hexadecimal representation for both uppercase and lowercase spellings.