1 * ICP DAS LP-8841 SPI Controller for RTC
2
3 ICP DAS LP-8841 contains a DS-1302 RTC. RTC is connected to an IO
4 memory register, which acts as an SPI master device.
5
6 The device uses the standard MicroWire half-duplex transfer timing.
7 Master output is set on low clock and sensed by the RTC on the rising
8 edge. Master input is set by the RTC on the trailing edge and is sensed
9 by the master on low clock.
10
11 Required properties:
12
13 - #address-cells: should be 1
14
15 - #size-cells: should be 0
16
17 - compatible: should be "icpdas,lp8841-spi-rtc"
18
19 - reg: should provide IO memory address
20
21 Requirements to SPI slave nodes:
22
23 - There can be only one slave device.
24
25 - The spi slave node should claim the following flags which are
26 required by the spi controller.
27
28 - spi-3wire: The master itself has only 3 wire. It cannor work in
29 full duplex mode.
30
31 - spi-cs-high: DS-1302 has active high chip select line. The master
32 doesn't support active low.
33
34 - spi-lsb-first: DS-1302 requires least significant bit first
35 transfers. The master only support this type of bit ordering.
36
37
38 Example:
39
40 spi@901c {
41 #address-cells = <1>;
42 #size-cells = <0>;
43 compatible = "icpdas,lp8841-spi-rtc";
44 reg = <0x901c 0x1>;
45
46 rtc@0 {
47 compatible = "maxim,ds1302";
48 reg = <0>;
49 spi-max-frequency = <500000>;
50 spi-3wire;
51 spi-lsb-first;
52 spi-cs-high;
53 };
54 };
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