Digilent 410-218P-KIT - Manual

P P m m o o d d R R T T C C C C ™ ™
R R e e f f e e r r e e n n c c e e M M a a n n u u a a l l
Revision: October 17, 2011
Note: This document applies to REV A of the board.
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Doc: 502-218 page 1 of 2
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Overview
The PmodRTCC is a real-time clock/calendar
powered by the Microchip MCP79410.
Features include:
•
a real-time clock/calendar with lithium
coin cell back-up
• an I
2
C interface
•
multi-function pin output that can
generate a square wave
•
two available alarms
•
128 bytes EEPROM
• 64 bytes SRAM
Functional Description
The PmodRTCC can communicate using I
2 C
via the 8-pin header J2. Digilent boards
implement several different I
2 C interfaces. For
more information, see the Connecting I 2 C
Interfaces document available at
www.digilentinc.com .
Interface
All communications with the device must
specify whether to write to the EEPROM or the
RTCC registers/SRAM, as well as a register
address and a flag indicating whether the
communication is a read or a write. This is
followed by the actual data transfer.
The PmodRTCC responds to two I
2 C
addresses. Address ‘1010111’ is used for
access to the EEPROM, and address
‘1101111’ is used for access to RTCC
registers/SRAM.
The device is configured by writing to the
registers within the device. The time registers
can be set to specific values and a control
register sets their functionality.
A full list of registers and their functionality, as
well as communication specifications, can be
found in the MCP79410 datasheet available at
the Microchip website.
The I
2 C interface standard uses two signal
lines. These are I2C data (SDA) and serial
clock (SCLK). These signals map to the serial
data (SDA) and serial clock (SCLK) on the
MCP79410.
Power Back-up
The PmodRTCC has a holder for a 12mm
lithium coin cell to power the RTCC and SRAM
if VDD should ever fall below the operating
point. In order to enable this power back-up,
the VBATEN bit must be set in the RTCC
registers. Compatible coin cells include
BR1216, CR1216, BR1220, CL1220, CR1220,
and BR1225.
Connector J2 – I2C Communications
Pin
Signal Description
1, 2 SCL I2C Clock
3, 4 SDA I2C Data
5, 6 GND Power Supply Ground
7, 8 VCC Power Supply (3.3V)