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Commit | Line | Data |
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7ecbfff6 SI |
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 | }; |