The Button/LED Controller Peripheral interface consists of 5 user accessible registers:
|BASE+00||LEDLATCH||16||LED control and real time status|
|BASE+02||LEDON||16||Set LED ON|
|BASE+04||LEDOFF||16||Set LED OFF|
|BASE+06||BTNSTATUS||16||Real time status of all buttons|
|BASE+08||BTNINTCONTROL||16||Interrupt control and status of all buttons|
Base address is defined by the bus controller in higher hierarchy of HDL code. All these registers are 16-bit wide. For 8-bit access, above registers are broken into two 8-bit registers each with suffixes 'L' and 'H' for low and high bytes respectively.
The LED latch register controls each of the LEDs (one bit per LED). It can also be read to get the status of the LEDs. If a bit is '1', the LED is on, else it is off. One or more of the bits are also updated by writing to the LEDON and LEDOFF registers.
|0||LEDLATCH1||R/W||LED 1 Status|
|1||LEDLATCH2||R/W||LED 2 Status|
|2||LEDLATCH3||R/W||LED 3 Status|
|3||LEDLATCH4||R/W||LED 4 Status|
This write-only register switches ON one or more LEDs independently. The bits where '1's are written will switch on the corresponding LEDs. A '0' has no effect. The corresponding bits in the LEDLATCH register are then updated.
|0||LEDON1||W||Turn on LED 1|
|1||LEDON2||W||Turn on LED 2|
|2||LEDON3||W||Turn on LED 3|
|3||LEDON4||W||Turn on LED 4|
This write-only register switches OFF one or more LEDs independently. The bits where '1's are written will switch off the corresponding LEDs. A '0' has no effect. The corresponding bits in the LEDLATCH register are then updated.
|0||LEDOFF1||W||Turn off LED 1|
|1||LEDOFF2||W||Turn off LED 2|
|2||LEDOFF3||W||Turn off LED 3|
|3||LEDOFF4||W||Turn off LED 4|
This read-only register shows the real time status of the buttons.
|0||BUTTON1||R||Button 1 status|
|1||BUTTON2||R||Button 2 status|
|2||BUTTON3||R||Button 3 status|
|3||BUTTON4||R||Button 4 status|
This register controls the interrupts after button press events. SW needs to clear bits 1 to 4 after servicing the interrupt.
|0||BTNIE||R/W||Button Interrupt Enable|
|1||BTNINT1||R/W||Button 1 Interrupt Status|
|2||BTNINT2||R/W||Button 2 Interrupt Status|
|3||BTNINT3||R/W||Button 3 Interrupt Status|
|4||BTNINT4||R/W||Button 4 Interrupt Status|
This code is released under the Creative Commons Attribution license. Please give attribution to the original author and Gadget Factory (www.gadgetfactory.net).
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