m41t94 STMicroelectronics, m41t94 Datasheet - Page 13

• Manufacturer Part Number: m41t94
• Description: Serial Real-time Clock With 44 Bytes Nvram And Reset
• Manufacturer: STMicroelectronics

3.1
Figure 7.
E
SCL
SDI
SDO
SPI bus characteristics
The Serial Peripheral interface (SPI) bus is intended for synchronous communication
between different ICs. It consists of four signal lines: Serial data input (SDI), Serial data
output (SDO), Serial clock (SCL) and a Chip Enable (E).
By definition a device that gives out a message is called “transmitter,” the receiving device
that gets the message is called “receiver.” The device that controls the message is called
“master.” The devices that are controlled by the master are called “slaves.”
The E input is used to initiate and terminate a data transfer. The SCL input is used to
synchronize data transfer between the master (micro) and the slave (M41T94) devices.
The SCL input, which is generated by the microcontroller, is active only during address and
data transfer to any device on the SPI bus (see
The M41T94 can be driven by a microcontroller with its SPI peripheral running in either of
the two following modes:
●
●
For these two modes, input data (SDI) is latched in by the low-to-high transition of clock
SCL, and output data (SDO) is shifted out on the high-to-low transition of SCL (see
on page 10
There is one clock for each bit transferred. Address and data bits are transferred in groups
of eight bits. Due to memory size the second most significant address bit is a Don’t Care
(address bit 6).
Input timing requirements
(CPOL, CPHA) = ('0', '0') or
(CPOL, CPHA) = ('1', '1').
tDVCH
and
Figure 6 on page
MSB IN
HIGH IMPEDANCE
tELCH
tCHDX
10).
tDLDH
tDHDL
tCLCH
Figure 5 on page
tCHEH
LSB IN
tCHCL
tEHEL
9).
tEHCH
AI04633
Table 2
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