Function uart_read

core/uart.c:256–368

Read from the 0xE000 range of ports */

/* Read from the 0xE000 range of ports */
static uint8_t uart_read(const uint16_t pio, bool peek) {
    uint8_t value;

    switch (pio) {
        case 0x00:
            if (uart.lcr >> 7 & 1) {
                value = uart.divisor & 0xFF;
            } else if (uart.rfve) {
                /* FIFO read */
                size_t index = uart.rfvi & (UART_FIFO_DEPTH - 1);
                value = uart.rxfifo[index];
                if (!peek) {
                    /* Remove the error status tracking from the FIFO */
                    if (uart.rxstat[index]) {
                        if (--uart.rxstatCount == 0) {
                            uart.lsr &= ~(1 << 7);
                        }
                    }
                    uart.rfvi++;
                    if (--uart.rfve) {
                        /* Indicate error status from the next FIFO entry */
                        index = uart.rxstat[uart.rfvi & (UART_FIFO_DEPTH - 1)];
                        uart.lsr |= uart.rxstat[index];
                        uart.isr |= (uart.rxstat[index] != 0) << 2;
                    } else {
                        /* Indicate empty FIFO */
                        uart.lsr &= ~(1 << 0);
                    }
                    /* Reset the timeout status and interrupt based on the new FIFO state */
                    uart_reset_rx_timeout();
                    uart_update_rxfifo_trigger();
                    intrpt_set(INT_UART, uart.ier & uart.isr);
                }
            } else {
                /* Empty FIFO */
                value = 0;
            }
            break;
        case 0x04:
            if (uart.lcr >> 7 & 1) {
                value = uart.divisor >> 8;
            } else {
                value = uart.ier;
            }
            break;
        case 0x08:
            /* Determine interrupt by priority */
            value = uart.ier & uart.isr;
            if (value >> 2 & 1) {
                /* Receiver Line Status */
                value = 6;
            } else if (value >> 0 & 1) {
                /* Received Data Available / Timeout */
                value = 4 | uart.rxTimeout << 3;
            } else if (value >> 1 & 1) {
                /* Transmitter Holding Register Empty */
                uart.isr &= ~(1 << 1);
                intrpt_set(INT_UART, value & ~(1 << 1));