PCF8563 — real-time clock¶
Supported
A driver ships with inoCORE. This part can be used today.
What it does¶
Keeps the date and time while the machine is switched off, on a coin cell. With it, alarms and the diagnostic buffer carry the real time instead of a count of seconds since the panel last started.
Fitted on the board, it is a system service: nothing is configured in a project, the time simply exists. See system services.
Parameters¶
| Keeps | Date and time |
| Backup | A coin cell, typically CR1220 |
| Interface | I²C |
Bus and addressing¶
I²C, address 0x51, fixed.
Wiring¶
Power, ground, SDA, SCL, a watch crystal and the backup cell. The crystal is the fussy part: it wants short tracks and no noise beside it, or the clock drifts.
Setting the time¶
Two ways, both described under system services:
- from a PC over the service cable;
- from WebVisu, which takes the time from the phone or computer viewing it.
Traps¶
| Trap | What to do |
|---|---|
| Flat backup cell | The time restarts at 2000-01-01 on every power-up. The diagnostics report it — believe them, and change the cell. |
| Expecting time zones | The panel keeps local time and knows nothing about zones or daylight saving. When the clocks change, set it as you would set the machine. |