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14.6.3 Microwire frame format
The Microwire format uses a special master/slave messaging method, which operates in half-duplex mode.
In this mode, when a frame begins, an 8-bit control message is transmitted to the slave. During this transmis-
sion, no incoming data is received by the SSP. After the message has been transmitted, the slave decodes it,
and after waiting one serial clock after the last bit of the 8-bit control message has been sent, it responds
with the requested data. The returned data can be 4 to 16 bits in length, making the total frame length any-
where from 13 to 25 bits.
8bit
MSB
LSB
Hi-Z(Note1
㸧
Hi-Z(Note1
㸧
Hi-Z(Note2
㸧
MSB
Hi-Z(Note2
㸧
LSB
4 to 16bit
SPCLK
SPFSS
SPDO
SPDI
Figure 14-6 Microwire frame format (single transfer)
Note 1: When transmission is disabled, SPDO terminal doesn't output and is high impedance status. This terminal
needs to add suitable pull-up/down resistance to fix the voltage level.
Note 2: SPDI terminal is always input and internal gate is open. In case of transmission signal will be high impedance sta-
tus, this terminal needs to add suitable pull-up/down resistance to fix the voltage level.
Though the Microwire format is similar to the SPI format, it uses the master/slave message transmission meth-
od for half-duplex communications. Each serial transmission is started by an 8-bit control word, which is
sent to the off-chip slave device. During this transmission, the SSP does not receive input data. After the mes-
sage has been transmitted, the off-chip slave decodes it, and after waiting one serial clock after the last bit of
the 8-bit control message has been sent, responds with the requested data. The returned data can be 4 to 16
bits in length, making the total frame length anywhere from 13 to 25 bits. With this configuration, during the
idle period:
・
The SPCLK signal is set to "Low".
・
SPFSS is set to "High".
・
The transmit data line SPDO is set to "Low".
A transmission is triggered by writing a control byte to the transmit FIFO. The falling edge of SPFSS cau-
ses the value stored in the bottom entry of the transmit FIFO to be transferred to the serial shift register for
the transmit logic, and the MSB of the 8-bit control frame to be shifted out onto the SPDO pin.
SPFSS remains "Low" and the SPDI pin remains tristated during this transmission. The off-chip serial
slave device latches each control bit into its serial shifter on the rising edge of each SPCLK.
After the last bit is latched by the slave device, the control byte is decoded during a one clock wait-state,
and the slave responds by transmitting data back to the SSP. Each bit is driven onto SPDI line on the falling
edge of SPCLK.
The SSP in turn latches each bit on the rising edge of SPCLK. At the end of the frame, for single trans-
fers, the SPFSS signal is pulled "High" one clock period after the last bit has been latched in the receive seri-
al shifter, which causes the data to be transferred to the receive FIFO.
TMPM3V6/M3V4
14. Synchronous Serial Port (SSP)
14.6 Frame Format
Page 330
2019-02-06
Summary of Contents for TMPM3V4
Page 1: ...32 Bit RISC Microcontroller TX03 Series TMPM3V6 M3V4 ...
Page 2: ... 2019 Toshiba Electronic Devices Storage Corporation ...
Page 7: ...Revision History Date Revision Comment 2019 02 06 1 First Release ...
Page 8: ......
Page 22: ...xiv ...
Page 52: ...TMPM3V6 M3V4 3 Processor Core 3 6 Exclusive access Page 30 2019 02 06 ...
Page 148: ...TMPM3V6 M3V4 7 Exceptions 7 6 Exception Interrupt Related Registers Page 126 2019 02 06 ...
Page 178: ...TMPM3V6 M3V4 9 Input Output port 9 2 Block Diagrams of Ports Page 156 2019 02 06 ...
Page 354: ...TMPM3V6 M3V4 14 Synchronous Serial Port SSP 14 6 Frame Format Page 332 2019 02 06 ...
Page 419: ...TMPM3V6 M3V4 Page 397 2019 02 06 ...
Page 462: ...TMPM3V6 M3V4 21 Watchdog Timer WDT 21 5 Control register Page 440 2019 02 06 ...
Page 544: ......