0001 * ICP DAS LP-8841 SPI Controller for RTC
0002
0003 ICP DAS LP-8841 contains a DS-1302 RTC. RTC is connected to an IO
0004 memory register, which acts as an SPI master device.
0005
0006 The device uses the standard MicroWire half-duplex transfer timing.
0007 Master output is set on low clock and sensed by the RTC on the rising
0008 edge. Master input is set by the RTC on the trailing edge and is sensed
0009 by the master on low clock.
0010
0011 Required properties:
0012
0013 - #address-cells: should be 1
0014
0015 - #size-cells: should be 0
0016
0017 - compatible: should be "icpdas,lp8841-spi-rtc"
0018
0019 - reg: should provide IO memory address
0020
0021 Requirements to SPI slave nodes:
0022
0023 - There can be only one slave device.
0024
0025 - The spi slave node should claim the following flags which are
0026 required by the spi controller.
0027
0028 - spi-3wire: The master itself has only 3 wire. It cannor work in
0029 full duplex mode.
0030
0031 - spi-cs-high: DS-1302 has active high chip select line. The master
0032 doesn't support active low.
0033
0034 - spi-lsb-first: DS-1302 requires least significant bit first
0035 transfers. The master only support this type of bit ordering.
0036
0037
0038 Example:
0039
0040 spi@901c {
0041 #address-cells = <1>;
0042 #size-cells = <0>;
0043 compatible = "icpdas,lp8841-spi-rtc";
0044 reg = <0x901c 0x1>;
0045
0046 rtc@0 {
0047 compatible = "maxim,ds1302";
0048 reg = <0>;
0049 spi-max-frequency = <500000>;
0050 spi-3wire;
0051 spi-lsb-first;
0052 spi-cs-high;
0053 };
0054 };
