Datasheet

 2012-2018 Microchip Technology Inc. DS20002300C-page 9
MCP7951X/MCP7952X
3.0 PIN DESCRIPTIONS
The descriptions of the pins are listed in Tab le 3- 1.
TABLE 3-1: PIN FUNCTION TABLE
3.1 Oscillator Input/Output (X1, X2)
These pins are used as the connections for an external
32.768 kHz quartz crystal and load capacitors. X1 is the
crystal oscillator input and X2 is the output. The
MCP795XX is designed to allow for the use of external
load capacitors in order to provide additional flexibility
when choosing external crystals. The MCP795XX is
optimized for crystals with a specified load capacitance
of 6-9 pF.
X1 also serves as the external clock input when the
MCP795XX is configured to use an external oscillator.
3.2 Backup Supply (VBAT)
This is the input for a backup supply to maintain the
RTCC and SRAM registers during the time when V
CC
is unavailable.
Power should be applied to VCC before VBAT.
If the battery backup feature is not being used, the
V
BAT pin should be connected to VSS.
3.3 Chip Select (CS)
A low level on this pin selects the device, whereas a
high level deselects the device. A nonvolatile memory
programming cycle which is already initiated or in
progress will be completed, regardless of the CS
input
signal. When the device is deselected, SO goes into
the high-impedance state, allowing multiple parts to
share the same SPI bus. After power-up, a high-to-low
transition on CS
is required prior to any sequence
being initiated.
3.4 Serial Input (SI)
This pin is used to transfer data into the device. It
receives instructions, addresses and data. Data is
latched on the rising edge of the serial clock.
3.5 Serial Output (SO)
This pin is used to transfer data out of the MCP795XX.
During a read cycle, data is shifted out on this pin after
the falling edge of the serial clock.
3.6 Serial Clock (SCK)
This pin is used to synchronize the communication
between a master and the MCP795XX. Instructions,
addresses or data present on the SI pin are latched on
the rising edge of the clock input, while data on the SO
pin is updated after the falling edge of the clock input.
3.7 Multifunction Pin (MFP)
The MFP pin is shared with the clock divider and the
alarms. This pin requires an external pull-up to V
CC or
V
BAT. The pin remains low until such time that the
interrupt flag in the register is cleared by software. This
pin has a maximum sink current of 10 mA.
Name
10-Pin
MSOP
10-Pin
TDFN
Pin Function
X1 1 1 Quartz Crystal Input, External Oscillator Input
X2 2 2 Quartz Crystal Output
V
BAT 3 3 Battery Backup Supply Input
CS
4 4 Chip Select Input
V
SS 5 5 Ground
SI 6 6 Serial Data Input
SO 7 7 Serial Data Output
SCK 8 8 Serial Clock Input
MFP 9 9 Multifunction Pin
V
CC 10 10 Primary Power Supply