icpdas-lp8841-spi-rtc.txt

 1* ICP DAS LP-8841 SPI Controller for RTC
 2
 3ICP DAS LP-8841 contains a DS-1302 RTC. RTC is connected to an IO
 4memory register, which acts as an SPI master device.
 5
 6The device uses the standard MicroWire half-duplex transfer timing.
 7Master output is set on low clock and sensed by the RTC on the rising
 8edge. Master input is set by the RTC on the trailing edge and is sensed
 9by the master on low clock.
10
11Required 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
21Requirements 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
38Example:
39
40spi@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};