- SS-HQ1 Application Notes -
Ver.1.0.0 January 7, 2005
232
Note
"L" and "H" of SIFSEL are recognized only during initial operation.
If they are changed, be sure to reset the system.
12.4.2. Communication Protocol with External Microcomputers
Communication Speed
Keep the transfer rate at 400 kbps or less (1SCK > 2.5[us]).
The required transfer rate is such that 32-byte transmissions are less than [1 field - communication prohibited
period].
Communication Timing
The CXD3172AR loads data in 8-bit units at the rising edge of SCK when XCS is low. The serial output is sent at
the falling edge of SCK in synchronization with the serial input. You must leave at least SCK 1 clock division
between byte data. The communication data is LSB first. Additionally, make SCK "H" (or pull-up) before making
XCS low.
For details on data strings, see the following sections on command specifications and the communication
format.
Fig 12.4-2 Communication Timing (External Microcomputers)
SCK
XCS
SI
1SCK(min)
1
2
6
7
8
D0 D1
D6 D7
D0 D1
D6 D7
1
2
6
7
8
SO
D0 D1
D6 D7
D0 D1
D6 D7
Hi-Z
Hi-Z
<BYTE1>
<BYTE N>