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}; 55