ST72C254G2M6 STMicroelectronics, ST72C254G2M6 Datasheet - Page 64

• Manufacturer Part Number: ST72C254G2M6
• Description: IC MCU 8BIT 8K FLASH SOIC-28
• Manufacturer: STMicroelectronics
• Series: ST7r

Specifications of ST72C254G2M6

• Core Processor: ST7
• Core Size: 8-Bit
• Speed: 16MHz
• Connectivity: I²C, SPI
• Peripherals: LVD, POR, PWM, WDT
• Number Of I /o: 22
• Program Memory Size: 8KB (8K x 8)
• Program Memory Type: FLASH
• Ram Size: 256 x 8
• Voltage - Supply (vcc/vdd): 3.2 V ~ 5.5 V
• Data Converters: A/D 6x8b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 28-SOIC (7.5mm Width)
• Controller Family/series: ST7
• No. Of I/o's: 22
• Ram Memory Size: 256Byte
• Cpu Speed: 8MHz
• No. Of Timers: 2
• Rohs Compliant: Yes
• Processor Series: ST72C2x
• Core: ST7
• Data Bus Width: 8 bit
• Data Ram Size: 256 B
• Interface Type: I2C, SPI
• Maximum Clock Frequency: 16 MHz
• Number Of Programmable I/os: 22
• Number Of Timers: 3 bit
• Operating Supply Voltage: 3.2 V to 5.5 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Development Tools By Supplier: ST7MDT1-DVP2/US
• Minimum Operating Temperature: - 40 C
• On-chip Adc: 8 bit
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Lead Free Status / Rohs Status: In Transition

ST72104G, ST72215G, ST72216G, ST72254G
SERIAL PERIPHERAL INTERFACE (Cont’d)
12.3.4.3 Data Transfer Format
During an SPI transfer, data is simultaneously
transmitted (shifted out serially) and received
(shifted in serially). The serial clock is used to syn-
chronize the data transfer during a sequence of
eight clock pulses.
The SS pin allows individual selection of a slave
device; the other slave devices that are not select-
ed do not interfere with the SPI transfer.
Clock Phase and Clock Polarity
Four possible timing relationships may be chosen
by software, using the CPOL and CPHA bits.
The CPOL (clock polarity) bit controls the steady
state value of the clock when no data is being
transferred. This bit affects both master and slave
modes.
The combination between the CPOL and CPHA
(clock phase) bits selects the data capture clock
edge.
Figure
combinations of the CPHA and CPOL bits. The di-
agram may be interpreted as a master or slave
timing diagram where the SCK pin, the MISO pin,
the MOSI pin are directly connected between the
master and the slave device.
The SS pin is the slave device select input and can
be driven by the master device.
Figure 39. CPHA / SS Timing Diagram
64/140
40, shows an SPI transfer with the four
MOSI/MISO
Master
(CPHA=0)
(CPHA=1)
Slave
Slave
SS
SS
SS
Byte 1
The master device applies data to its MOSI pin-
clock edge before the capture clock edge.
CPHA bit is set
The second edge on the SCK pin (falling edge if
the CPOL bit is reset, rising edge if the CPOL bit is
set) is the MSBit capture strobe. Data is latched on
the occurrence of the second clock transition.
No write collision should occur even if the SS pin
stays low during a transfer of several bytes (see
Figure
CPHA bit is reset
The first edge on the SCK pin (falling edge if CPOL
bit is set, rising edge if CPOL bit is reset) is the
MSBit capture strobe. Data is latched on the oc-
currence of the first clock transition.
The SS pin must be toggled high and low between
each byte transmitted (see
To protect the transmission from a write collision a
low value on the SS pin of a slave device freezes
the data in its DR register and does not allow it to
be altered. Therefore the SS pin must be high to
write a new data byte in the DR without producing
a write collision.
Byte 2
39).
Byte 3
Figure
39).
VR02131A