====== Pmod RTCC Reference Manual ======
The Digilent Pmod RTCC (Revision A) is a real time clock and calendar module with battery backup capabilities. 

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== Download This Reference Manual ==
  * {{:reference:pmod:pmodrtcc:pmodrtcc_rm.pdf| PDF}}

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===== Features =====
  * Real-time clock/calendar with lithium coin cell back-up
  * Multi-function pin output that can generate a square wave
  * Two available alarms
  * 128 bytes %%EEPROM%%
  * 64 bytes SRAM
  * 2×4-pin connector with I2C interface

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=====Functional Description =====
The %%Pmod RTCC%% utilizes Microchip's [[http://ww1.microchip.com/downloads/en/DeviceDoc/22266d.pdf|MCP74910]] to provide accurate time-keeping and alarm configuration for any long-term (or short-term) project.

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===== Interfacing with the Pmod=====
The %%Pmod RTCC%% communicates with the host board via the [[pmod:communication_protocols:i2c|I²C protocol]]. By sending the Pmod a control byte of '1101111X', where X indicates a read (1) or a write (0) operation, users may program the module with both the current time as well as configuring the two alarms.

As the %%Pmod RTCC%% operates both as a real time clock, a calendar, and an alarm, users may have it simply act as analog clock by having it output a 1 Hz square wave. Alternatively, the module could be configured to chime every every hour or to let you know when it is your birthday.

==== Pinout Description Table ====
^  Pin    ^  Signal  ^  Description             ^
|  1 & 5  |  SCL     |  Serial Clock            |
|  2 & 6  |  SDA     |  Serial Data             |
|  3 & 7  |  GND     |  Power Supply Ground     |
|  4 & 8  |  VCC     |  Power Supply (3.3V/5V)  |


Any external power applied to the %%Pmod RTCC%% must be within 1.8V and 5.5V; however, it is recommended that Pmod is operated at 3.3V.

The %%Pmod RTCC%% is also able to run off of a coin cell battery and automatically switch to using battery power when Vcc drops below approximately 1.5V. 
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===== Physical Dimensions =====
The pins on the pin header are spaced 100 mil apart. The PCB is 1.3 inches long on the sides parallel to the pins on the pin header and 0.8 inches long on the sides perpendicular to the pin header.
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===== Additional Information =====
The schematics of the %%Pmod RTCC%% are available {{pmod:pmod:pmodrtcc_sch.pdf|here}}. Additional information about the %%MCP79410%% including communication modes and specific timings of the chip can be found by checking out its datasheet [[http://ww1.microchip.com/downloads/en/DeviceDoc/20002266F.pdf|here]]. 

Example code demonstrating how to get information from the %%Pmod RTCC%% can be found [[pmod:pmodrtcc:start#example_projects|here]]. 

If you have any questions or comments about the %%Pmod RTCC%%, feel free to post them under the appropriate section ("Add-on Boards") of the [[https://forum.digilent.com/|Digilent Forum]].