TMP86FS23UG datasheet(156/252 Pages) TOSHIBA

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Page 144

12. Synchronous Serial Interface (SIO)

12.6 Transfer Mode

TMP86FS23UG

Figure 12-6 Number of words to transfer (Example: 1word = 4bit)

12.6 Transfer Mode

SIOCR1<SIOM> is used to select the transmit, receive, or transmit/receive mode.

12.6.1 4-bit and 8-bit transfer modes

In these modes, firstly set the SIO control register to the transmit mode, and then write first transmit data

(number of transfer words to be transferred) to the data buffer registers (DBR).

After the data are written, the transmission is started by setting SIOCR1<SIOS> to “1”. The data are then

output sequentially to the SO pin in synchronous with the serial clock, starting with the least significant bit

(LSB). As soon as the LSB has been output, the data are transferred from the data buffer register to the shift

empty) interrupt is generated to request the next transmitted data.

When the internal clock is used, the serial clock will stop and an automatic-wait will be initiated if the next

transmitted data are not loaded to the data buffer register by the time the number of data words specified with

the SIOCR2<BUF> has been transmitted. Writing even one word of data cancels the automatic-wait; therefore,

when transmitting two or more words, always write the next word before transmission of the previous word is

completed.

Note:Automatic waits are also canceled by writing to a DBR not being used as a transmit data buffer register; there-

fore, during SIO do not use such DBR for other applications. For example, when 3 words are transmitted, do

not use the DBR of the remained 5 words.

When an external clock is used, the data must be written to the data buffer register before shifting next data.

Thus, the transfer speed is determined by the maximum delay time from the generation of the interrupt request

to writing of the data to the data buffer register by the interrupt service program.

The transmission is ended by clearing SIOCR1<SIOS> to “0” or setting SIOCR1<SIOINH> to “1” in buffer

empty interrupt service program.

(a) 1 word transmit

(b) 3 words transmit

SO pin

INTSIO interrupt

SO pin

SI pin

SCK pin

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