//  Template file with defines of peripheral registers
//  QtMips simulator https://github.com/cvut/QtMips/
//  developed by Karel Koci and Pavel Pisa.
//
//  template.S       - example file
//
//  (C) 2019 by Pavel Pisa
//      e-mail:   pisa@cmp.felk.cvut.cz
//      homepage: http://cmp.felk.cvut.cz/~pisa
//      work:     http://www.pikron.com/
//      license:  public domain

.globl _start
.globl __start
.set noreorder
.ent _start

// Serial port/terminal registers
// There is mirror of this region at address 0xffff0000
// to match QtSpim and Mars emulators

.equ SERIAL_PORT_BASE,      0xffffc000 // base address of serial port region

.equ SERP_RX_ST_REG,        0xffffc000 // Receiver status register
.equ SERP_RX_ST_REG_o,          0x0000 // Offset of RX_ST_REG
.equ SERP_RX_ST_REG_READY_m,       0x1 // Data byte is ready to be read
.equ SERP_RX_ST_REG_IE_m,          0x2 // Enable Rx ready interrupt

.equ SERP_RX_DATA_REG,      0xffffc004 // Received data byte in 8 LSB bits
.equ SERP_RX_DATA_REG_o,        0x0004 // Offset of RX_DATA_REG

.equ SERP_TX_ST_REG,        0xffffc008 // Transmitter status register
.equ SERP_TX_ST_REG_o,          0x0008 // Offset of TX_ST_REG
.equ SERP_TX_ST_REG_READY_m,       0x1 // Transmitter can accept next byte
.equ SERP_TX_ST_REG_IE_m,          0x2 // Enable Tx ready interrupt

.equ SERP_TX_DATA_REG,      0xffffc00c // Write word to send 8 LSB bits to terminal
.equ SERP_TX_DATA_REG_o,        0x000c // Offset of TX_DATA_REG


// Memory mapped peripheral for dial knobs input,
// LED and RGB LEDs output designed to match
// MZ_APO education Zynq based board developed
// by Petr Porazil and Pavel Pisa at PiKRON.com company

.equ SPILED_REG_BASE        0xffffc100 // base of SPILED port region

.equ SPILED_REG_LED_LINE,   0xffffc104 // 32 bit word mapped as output
.equ SPILED_REG_LED_LINE_o,     0x0004 // Offset of the LED_LINE
.equ SPILED_REG_LED_RGB1,   0xffffc110 // RGB LED 1 color components
.equ SPILED_REG_LED_RGB1_o,     0x0010 // Offset of LED_RGB1
.equ SPILED_REG_LED_RGB2,   0xffffc114 // RGB LED 2 color components
.equ SPILED_REG_LED_RGB2_o,     0x0014 // Offset of LED_RGB2
.equ SPILED_REG_KNOBS_8BIT, 0xffffc124 // Three 8 bit knob values
.equ SPILED_REG_KNOBS_8BIT_o,   0x0024 // Offset of KNOBS_8BIT

// The simple 16-bit per pixel (RGB565) frame-buffer
// display size is 480 x 320 pixel
// Pixel format RGB565 expect
//   bits 11 .. 15 red component
//   bits  5 .. 10 green component
//   bits  0 ..  4 blue component
.equ LCD_FB_START,          0xffe00000
.equ LCD_FB_END,            0xffe4afff

// Mapping of interrupts
// Irq number   Cause/Status Bit   Source
//  2 / HW0      10                Serial port ready to accept character to Tx
//  3 / HW1      11                There is received character ready to be read
//  7 / HW5      15                Counter reached value in Compare register


// Linux kernel compatible system calls subset

.equ __NR_exit,     4001	// void exit(int status)
.equ __NR_read,     4003	// ssize_t read(int fd, void *buf, size_t count)
.equ __NR_write,    4004	// ssize_t write(int fd, const void *buf, size_t count)
.equ __NR_close,    4006	// int close(int fd)
.equ __NR_open,     4005	// int open(const char *pathname, int flags, mode_t mode)
.equ __NR_brk,      4045	// void * brk(void *addr)
.equ __NR_truncate, 4092	// int ftruncate(int fd, off_t length)
.equ __NR_readv,    4145	// ssize_t readv(int fd, const struct iovec *iov, int iovcnt)
.equ __NR_writev,   4146	// ssize_t writev(int fd, const struct iovec *iov, int iovcnt)
.equ __NR_set_thread_area, 4283 // int set_thread_area(unsigned long addr)

// Original MIPS start address after reset
.org    0x80020000

.text

__start:
_start:

	addi	$v0, $zero, __NR_write
	addi	$a0, $zero, 1
	la	$a1, text_1
	addi	$a2, $zero, text_1_e - text_1
	syscall

	addi	$v0, $zero, __NR_exit
	addi	$a0, $zero, 0

final:	break
	beq	$zero, $zero, final
	nop

.end _start

.data

data_1:	.word	1, 2, 3, 4

text_1:	.ascii	"Hello word.\n"	// store ASCII text, no termination
text_1_e: