Siemens AC75 - Manual (Page 498)

AC75 AT Command Set
19.8 AT^SSPI
s
AC75_ATC_V01.002 Page 498 of 569 10/30/06
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19.8.1 Specifying Delay Time for I²C
The following figures are provided to assist you in specifying appropriate values for the parameters
and . All delays are relative to the data transfer rate. To calculate the delay use the formula and the
values given below.
Table 19.2: Values for calculating the delay
Subparameter Bit Hexadecimal Selected function
SPI mode D15 - D12 0
1
2
3
Four different SPI modes. Phase and
polarity of all SPI modes are illustrated in
Section 19.8.2 , Selecting SPI Mode .
Chip Select (CS) mode D11 - D8 0 One Chip Select per Transfer Frame.
Arrangement of bytes D7 - D4 0 Big endian
Bit sequence
(arrangement of bits on the SPI)
D3 - D0 0 MSB first
Figure 19.1: Formula for calculating the delay
Parameter Values
Delay value Value set with parameter or
Master clock 13 MHz
Default data transfer rate 400 bps
User data transfer rate Value selected with subparameter data transfer rate within
tion>
, for example 100 kbps or 400 kbps
Delay_min for Write 7.4 µs at 100 kbps
2.0 µs at 400 kbps
Delay_min for Read 9.9 µs at 100 kbps
2.6 µs at 400 kbps
Figure 19.2: Delay time on I²C after Write