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Line 17:
Line 17: + + + + Line 22:
Line 26: − + − + − + − + − + + + + + − + − + − The values here are read from, stored in the AGB_FIRM [[3DS_Virtual_Console#NAND_Savegame|savegame]], and then written to the respective registers upon save loading. These registers are read after waiting for bit 15 of ARM7_?_STATUS to be set, writing 0x0 and then 0x2 to that register, and then waiting for bit 15 to be set again. If bit 14 is not set afterward, these registers are read from and stored in the save. Otherwise, these values are saved (and restored) as 0x0.+ + + + + + + + + + +
RTC is a guess, but what else is a hardware device with up to 0x8 stored at power-off?
| 0x10018080
| 0x10018080
| ?
| ?
|-
| ARM7_SAVE_MODE
| 0x10018100
| 0x2
|-
|-
| ARM7_?_CNT
| ARM7_?_CNT
| 0x2
| 0x2
|-
|-
| ARM7_?_STATUS
| ARM7_RTC_CNT?
| 0x10018108
| 0x10018108
| 0x2
| 0x2
|-
|-
| ARM7_?_WRITE_1
| ?
| 0x10018110
| 0x10018110
| 0x4
| 0x4
|-
|-
| ARM7_?_WRITE_2
| ?
| 0x10018114
| 0x10018114
| 0x4
| 0x4
|-
|-
| ARM7_?_READ_1
| ARM7_RTC_LO?
| 0x10018118
| 0x10018118
| 0x4
| 0x4
|-
|-
| ARM7_?_READ_2
| ARM7_RTC_HI?
| 0x1001811C
| 0x1001811C
| 0x4
| 0x4
|-
| ARM7_SAVE_CFG
| 0x10018120
| 0x10
|}
|}
== ARM7_CNT ==
== ARM7_CNT ==
This indicates (controls?) the mode of the ARM7. 1 = TWL, 2 = AGB.
This seems to control the mode of the ARM7. 1 = TWL, 2 = AGB.
== ARM7_CODE ==
== ARM7_CODE ==
This is the first code that will be run after execution begins. TwlProcess9 uses this to put ARM7 in a loop (TWL), and to set the POSTFLG and branch to more copied code (AGB).This doesn't seem to start execution by itself.
This is the first code that will be run after execution begins. TwlProcess9 uses this to put ARM7 in a loop (TWL), and to set the POSTFLG and branch to more copied code (AGB).This doesn't seem to start execution by itself.
== ARM7_?_READ/WRITE ==
== ARM7_SAVE_MODE ==
This tells the save storage emulation hardware which device type to emulate (EEPROM, 512k flash, and SRAM are all that have been spotted). This comes directly from the [[3DS_Virtual_Console#Footer|ROM footer]].
== ARM7_RTC(?) ==
These registers may be used to control a realtime clock. To set or read the data here, first ARM7_RTC_CNT's bit 15 is waited on. Next ARM7_RTC_CNT is set to zero.
For a write: the two registers are written, a 1 is written to ARM7_RTC_CNT, and it is waited on the same as before. Afterwards if bit 14 is not set in ARM7_RTC_CNT, the value was set successfully.
For a read: a 2 is written to ARM7_RTC_CNT, it's waited on again. Afterwards, if bit 14 is not set, the RTC can be read. Presumably the hardware can be re-enabled by writing a zero to ARM7_RTC_CNT at this point, but AGB_FIRM does not.
== ARM7_SAVE_CFG ==
This is copied from rom footer + 0x10. It presumably configures details about storage, such as IDs, and likely allows enabling the RTC for games which need it. Format of this data is unknown, and slightly difficult to determine without some hardware poking.
= Memory map =
= Memory map =