fm3316 Ramtron Corporation, fm3316 Datasheet - Page 2

• Manufacturer Part Number: fm3316
• Description: 3v Integrated Processor Companion With Memory
• Manufacturer: Ramtron Corporation

Pin Configuration
Pin Descriptions
Rev. 1.1
Dec. 2007
Pin Name
/CS
SCK
SI
SO
CNT
ACS
X1, X2
/RST
PFI
PFO
VBAK
VDD
VSS
VBAK
CNT
VSS
SO
CS
X1
X2
Supply
Supply
Supply
Output
Output
Output
Type
Input
Input
Input
Input
Input
I/O
I/O
1
2
3
4
5
6
7
Pin Description
Chip Select: This active low input activates the device. When high, the device enters low-
power standby mode, ignores the SCK and SI inputs, and the SO output is tri-stated.
When low, the device internally activates the SCK signal. A falling edge on /CS must
occur prior to every op-code.
Serial Clock: All I/O activity is synchronized to the serial clock. Inputs are latched on the
rising edge and outputs occur on the falling edge. Since the device is static, the clock
frequency may be any value between 0 and 16 MHz and may be interrupted at any time.
Serial Input: All data is input to the device on this pin. The pin is sampled on the rising
edge of SCK and is ignored at other times. It should always be driven to a valid logic level
to meet I
interface.
Serial Output: This is the data output pin. It is driven during a read and remains tri-stated
at all other times. Data transitions are driven on the falling edge of the serial clock. The
SO pin may be connected to SI for a single pin data interface.
Event Counter Input: This input increments the counter when an edge is detected on this
pin. The polarity is programmable and the counter value is nonvolatile or battery-backed,
depending on the mode. This pin should be tied to ground if unused.
Alarm/Calibration/SquareWave: This is an open-drain output that requires an external
pullup resistor. In normal operation, this pin acts as the active-low alarm output. In
Calibration mode, a 512 Hz square-wave is driven out. In SquareWave mode, the user
may select a frequency of 1, 512, 4096, or 32768 Hz to be used as a continuous output.
The SquareWave mode is entered by clearing the AL/SW and CAL bits in register 18h.
32.768 kHz crystal connection. When using an external oscillator, apply the clock to X1
and a DC mid-level to X2 (see Crystal Type section for suggestions).
Reset: This active-low output is open drain with weak pull-up. It is also an input when
used as a manual reset. This pin should be left floating if unused.
Early Power-fail Input: Typically connected to an unregulated power supply to detect an
early power failure. This pin must be tied to ground if unused.
Early Power-fail Output: This pin is the early power-fail output and is typically used to
drive a microcontroller NMI pin. PFO drives low when the PFI voltage is <1.5V.
Backup supply voltage: A 3V battery or a large value capacitor. If no backup supply is
used, this pin should be tied to V
Supply Voltage.
Ground
14
13
12
11
10
9
8
DD
specifications. The SI pin may be connected to SO for a single pin data
PFO
RST
PFI
ACS
SCK
VDD
SI
SS
and the VBC bit should be cleared.
Pin Name
/CS
SCK
SI
SO
PFI
PFO
CNT
ACS
/RST
X1, X2
VDD
VBAK
VSS
FM33256/FM3316 SPI Companion w/ FRAM
Function
Chip Select
Serial Clock
Serial Data Input
Serial Data Output
Power Fail Input
Power Fail Output (NMI)
Event Counter Input
Alarm/Calibration/SqWave
Reset Input/Output
Crystal Connections
Supply Voltage
Battery-Backup Supply
Ground
Page 2 of 28