FM25V10
data are then transferred. The CS must go inactive after an
operation is complete and before a new opcode can be issued.
The commonly used terms in the SPI protocol are as follows:
Functional Overview
The FM25V10 is a serial F-RAM memory. The memory array is
logically organized as 131,072 × 8 bits and is accessed using an
industry-standard serial peripheral interface (SPI) bus. The
functional operation of the F-RAM is similar to serial flash and
serial EEPROMs. The major difference between the FM25V10
and a serial flash or EEPROM with the same pinout is the
F-RAM's superior write performance, high endurance, and low
power consumption.
SPI Master
The SPI master device controls the operations on a SPI bus. An
SPI bus may have only one master with one or more slave
devices. All the slaves share the same SPI bus lines and the
master may select any of the slave devices using the CS pin. All
of the operations must be initiated by the master activating a
slave device by pulling the CS pin of the slave LOW. The master
also generates the SCK and all the data transmission on SI and
SO lines are synchronized with this clock.
Memory Architecture
When accessing the FM25V10, the user addresses 64K
locations of eight data bits each. These eight data bits are shifted
in or out serially. The addresses are accessed using the SPI
protocol, which includes a chip select (to permit multiple devices
on the bus), an opcode, and a three-byte address. The upper 7
bits of the address range are 'don't care' values. The complete
address of 17 bits specifies each byte address uniquely.
SPI Slave
The SPI slave device is activated by the master through the Chip
Select line. A slave device gets the SCK as an input from the SPI
master and all the communication is synchronized with this
clock. An SPI slave never initiates a communication on the SPI
bus and acts only on the instruction from the master.
Most functions of the FM25V10 are either controlled by the SPI
interface or handled by on-board circuitry. The access time for
the memory operation is essentially zero, beyond the time
needed for the serial protocol. That is, the memory is read or
written at the speed of the SPI bus. Unlike a serial flash or
EEPROM, it is not necessary to poll the device for a ready
condition because writes occur at bus speed. By the time a new
bus transaction can be shifted into the device, a write operation
is complete. This is explained in more detail in the interface
section.
The FM25V10 operates as an SPI slave and may share the SPI
bus with other SPI slave devices.
Chip Select (CS)
To select any slave device, the master needs to pull down the
corresponding CS pin. Any instruction can be issued to a slave
device only while the CS pin is LOW. When the device is not
selected, data through the SI pin is ignored and the serial output
pin (SO) remains in a high-impedance state.
Note A new instruction must begin with the falling edge of CS.
Therefore, only one opcode can be issued for each active Chip
Select cycle.
Serial Peripheral Interface – SPI Bus
The FM25V10 is a SPI slave device and operates at speeds up
to 40 MHz. This high-speed serial bus provides
high-performance serial communication to a SPI master. Many
common microcontrollers have hardware SPI ports allowing a
direct interface. It is quite simple to emulate the port using
ordinary port pins for microcontrollers that do not. The FM25V10
operates in SPI Mode 0 and 3.
Serial Clock (SCK)
The Serial Clock is generated by the SPI master and the
communication is synchronized with this clock after CS goes
LOW.
The FM25V10 enables SPI modes
0 and 3 for data
communication. In both of these modes, the inputs are latched
by the slave device on the rising edge of SCK and outputs are
issued on the falling edge. Therefore, the first rising edge of SCK
signifies the arrival of the first bit (MSB) of a SPI instruction on
the SI pin. Further, all data inputs and outputs are synchronized
with SCK.
SPI Overview
The SPI is a four-pin interface with Chip Select (CS), Serial Input
(SI), Serial Output (SO), and Serial Clock (SCK) pins.
The SPI is a synchronous serial interface, which uses clock and
data pins for memory access and supports multiple devices on
the data bus. A device on the SPI bus is activated using the CS
pin.
Data Transmission (SI/SO)
The SPI data bus consists of two lines, SI and SO, for serial data
communication. SI is also referred to as Master Out Slave In
(MOSI) and SO is referred to as Master In Slave Out (MISO). The
master issues instructions to the slave through the SI pin, while
the slave responds through the SO pin. Multiple slave devices
may share the SI and SO lines as described earlier.
The relationship between chip select, clock, and data is dictated
by the SPI mode. This device supports SPI modes 0 and 3. In
both of these modes, data is clocked into the F-RAM on the rising
edge of SCK starting from the first rising edge after CS goes
active.
The SPI protocol is controlled by opcodes. These opcodes
specify the commands from the bus master to the slave device.
After CS is activated, the first byte transferred from the bus
master is the opcode. Following the opcode, any addresses and
The FM25V10 has two separate pins for SI and SO, which can
be connected with the master as shown in Figure 3.
Document Number: 001-84499 Rev. *H
Page 4 of 25
5秒后页面跳转
AD637数据手册解读：主要特性、引脚及其功能解读、电气参数
ADUM1201资料手册解读：参数分析、引脚说明、应用分析
一文带你了解压敏电阻器在直流电路中的过压保护作用
可控硅触发板选型指南
微信公众号
抖音公众号
浙公网安备 33010502006866号 浙ICP备10014259号-119
营业执照ICP证
数据手册
如果您发现信息不准确，
