7643 datasheet(28/121 Pages) RENESAS

28 / 121 page

Rev.2.00

Aug 28, 2006

page 28 of 119

7643 Group

REJ03B0054-0200

Serial I/O Normal Operation

The serial I/O counter is set to “7” by writing operation to the serial

I/O shift register (address 002A16). When the SRDY Output Select

bit is “1”, the SRDY pin goes “L” after that writing. On the negative

edge of the transfer clock the SRDY pin returns “H” and the data

of the first bit is transmitted from the STXD pin. The remaining

data are done from the STXD pin bit by bit on each falling edge of

the transfer clock.

Additionally, the data is latched from the SRXD pin on each rising

edge of the transfer clock and then the contents of the serial I/O

shift register are shifted by one bit.

When the internal system clock is selected as the transfer clock,

the followings occur at counting eight transfer clocks:

•The serial I/O counter reaches “0”

•The transfer clock halts at “H”

•The serial I/O interrupt request bit is set to “1”

•The STXD pin goes a high-impedance state after an 8-bit transfer

is completed.

When the external clock is selected as the transfer clock, the fol-

lowings occur at counting eight transfer clocks:

•The serial I/O counter reaches “0”

•The serial I/O interrupt request bit is set to “1”

In this case, the transfer clock needs to be controlled by the exter-

nal source because the transfer clock does not halt. Additionally,

the STXD pin does not go a high-impedance state after an 8-bit

transfer is completed.

Figure 23 shows serial I/O timing.

Fig. 23 Serial I/O timing

First

Last

STXD/SRXD

Synchronizing clock

SCLK (CPoL = 1, CPha =1 )

SCLK (CPoL = 0, CPha = 1)

SCLK (CPoL = 1, CPha = 0)

SCLK (CPoL = 0, CPha = 0)

qNormal mode timing (LSB first)

Transfer clock

Synchronizing clock

Serial I/O shift

SRDY signal

Serial I/O output STXD

Serial I/O input SRXD

(Note)

Interrupt request bit is set to “1”.

Note: When the internal clock is selected as the transfer clock, the STXD pin goes to a high-impedance state after transfer completion.

qSPI compatible mode timing

SRDY signal

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