Added a quick command to lookup JEP106 IDs. It’s not yet in main, but I’ll do help/docs/etc tomorrow and push it. Any thoughts?
There are several formats of JEDEC manufacturer IDs. The one we run into most often is the two byte JEP106 ID.
[0][0x7e - 1] = "Numonyx Corporation",
[1][0x01 - 1] = "Cirrus Logic",
Byte 1 is the bank ID. That’s the first number in the array (0, 1 here). Currently the number uses at most the lower 4 bits (16 banks, numbered 0-15).
Byte 2 is the manufacturer ID. Here are some fun facts about manufacturer ID numbers:
- ID are 7 bits and 1 indexed (not 0!). So there are 126 IDs in each bank (0x1 to 0x7e)
- ID 0x00 is invalid (indexed from 1)
- IF the bank == 0 then ID bit 7 will be 0. Thus IDs in bank 0 range from 0x01 to 0x7e.
- IF the bank > 0 then ID bit 7 will be 1. Thus IDs in bank 1+ range from 0x81 to 0xff.
//error if bank = 0 and id bit 7 is set
if((bank == 0) && (id & 0x80)){
printf("Invalid JEP106 ID: bank 0 cannot have bit 7 set in device id\r\n");
return;
}
//error if bank > 0 and id bit 7 is clear
if((bank > 0) && !(id & 0x80)){
printf("Invalid JEP106 ID: bank > 0 must have bit 7 set in device id\r\n");
return;
}
This is our sanity check for ID numbers:
- Bank = 0 then ID bit 7 must also be 0.
- Bank > 0 then ID bit 7 must be 1.
bank=(bank & 0xf); //only lower 4 bits are valid for bank
id=(id & 0x7f); //SPD JEDEC ID is lower 7 bits, no parity bit. Bit 7 = 1 = bank > 0
Some prep is needed before we can lookup the manufacturer in the JEP106 table:
- bank & 0xf - Only use the lower four bits of bank
- id & 0x7f - zero out bit 7 of the ID and keep the lower 7 bits.
- id-- - subtract one to adjust the ID for the 0 indexed lookup array (not shown, done in the lower lookup function).
