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
Confidential / Released
19.8.1 Specifying Delay Time for I²C
The following figures are provided to assist you in specifying appropriate values for the parameters
<delayOne>
and
<delayTwo>
. 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
<delayOne>
or
<delayTwo>
Master clock 13 MHz
Default data transfer rate 400 bps
User data transfer rate Value selected with subparameter data transfer rate within
<basicConfigura-
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