so with the pull-ups that's that status of your pins
| LOW | HIGH | |
|---|---|---|
| CHRG | Charging | Not Charging |
| STDBY | Complete | Not Complete |
You want to detect whether charging is taking place and if the battery is fully charged.
Another way to represent this is
| CHRG | STDBY | state |
|---|---|---|
| LOW | LOW | impossible (can't be both charging and complete) |
| LOW | HIGH | Charging, not fully charged |
| HIGH | LOW | Not Charging, fully charged |
| HIGH | HIGH | impossible (can't be both not charging and not complete) |
so if the components can never be in the impossible situation then just looking at one of them you'll know what's the status.
eg if CHRG is LOW then you know it's Charging, not fully charged and if CHRG is HIGH then you know it's Not Charging which means fully charged