Philips CEM2100/00, Service Manual

Page: 285 / 430

Page 163
T
5CL8
(2) External clock
When an external clock is selected by setting SIO1CR<SCK> to “111B”, the clock via the
SCK1
pin from an external source is used as the serial clock.
To ensure shift operation, the serial clock pulse width must be 4/fc or more for both “H” and “L”
levels.
Figure 14-3 External Clock
14.3.1.2 Shift edge
The leading edge is used to transmit data, and the trailing edge is used to receive data.
(1)
Leading edge shift
Data is shifted on the leading edge of the serial clock (falling edge of the
SCK1
pin input/output).
(2)
Trailing edge shift
Data is shifted on the trailing edge of the serial clock (rising edge of the
SCK1
pin input/output).
Figure 14-4 Shift Edge
tSCKL tSCKH
tSCKL, tSCKH > 4/fc
SCK1
pin
7******* ********
Bit7
Shift out
***01234 **012345 *0123456
Bit5
Bit6
Bit5 Bit6 Bit7
67****** 567*****
(a) Leading edge shift (Example of MSB transfer)
(b) Trailing edge shift (Example of MSB transfer)
01234567 ****0123 *****012 ******01 *******0 ********
Bit4
4567**** 34567*** 234567** 1234567* 01234567
Bit4 Bit3 Bit2 Bit1 Bit0
Bit3 Bit2 Bit1 Bit0
SIO1CR<SIOS>
SCK1
pin
Shift register
SO1 pin
Shift register
SCK1
pin
SI1 pin
SIO1CR<SIOS>