esp-idf/components/esp32/include/xtensa/uart-16550.h

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uart-16550.h    Generic definitions for National Semiconductor 16550 UART

This is used by board-support-packages with one or more 16550 compatible UARTs.
A BSP provides a base address for each instance of a 16550 UART on the board.

Note that a 16552 DUART (Dual UART) is simply two instances of a 16550 UART.

*******************************************************************************/

#ifndef _UART_16550_H_
#define _UART_16550_H_

/* C interface to UART registers. */
struct uart_dev_s {
  union {
    uart16550_reg_t rxb;    /* DLAB=0: receive buffer, read-only */
    uart16550_reg_t txb;    /* DLAB=0: transmit buffer, write-only */
    uart16550_reg_t dll;    /* DLAB=1: divisor, LS byte latch */
  } w0;
  union {
    uart16550_reg_t ier;    /* DLAB=0: interrupt-enable register */
    uart16550_reg_t dlm;    /* DLAB=1: divisor, MS byte latch */
  } w1;

  union {
    uart16550_reg_t isr;    /* DLAB=0: interrupt status register, read-only */
    uart16550_reg_t fcr;    /* DLAB=0: FIFO control register, write-only */
    uart16550_reg_t afr;    /* DLAB=1: alternate function register */
  } w2;

  uart16550_reg_t lcr;      /* line control-register, write-only */
  uart16550_reg_t mcr;      /* modem control-regsiter, write-only */
  uart16550_reg_t lsr;      /* line status register, read-only */
  uart16550_reg_t msr;      /* modem status register, read-only */
  uart16550_reg_t scr;      /* scratch regsiter, read/write */
};


#define _RXB(u) ((u)->w0.rxb)
#define _TXB(u) ((u)->w0.txb)
#define _DLL(u) ((u)->w0.dll)
#define _IER(u) ((u)->w1.ier)
#define _DLM(u) ((u)->w1.dlm)
#define _ISR(u) ((u)->w2.isr)
#define _FCR(u) ((u)->w2.fcr)
#define _AFR(u) ((u)->w2.afr)
#define _LCR(u) ((u)->lcr)
#define _MCR(u) ((u)->mcr)
#define _LSR(u) ((u)->lsr)
#define _MSR(u) ((u)->msr)
#define _SCR(u) ((u)->scr)

typedef volatile struct uart_dev_s uart_dev_t;

/* IER bits */
#define RCVR_DATA_REG_INTENABLE 0x01
#define XMIT_HOLD_REG_INTENABLE 0x02
#define RCVR_STATUS_INTENABLE   0x04
#define MODEM_STATUS_INTENABLE  0x08

/* FCR bits */
#define _FIFO_ENABLE     0x01
#define RCVR_FIFO_RESET  0x02
#define XMIT_FIFO_RESET  0x04
#define DMA_MODE_SELECT  0x08
#define RCVR_TRIGGER_LSB 0x40
#define RCVR_TRIGGER_MSB 0x80

/* AFR bits */
#define AFR_CONC_WRITE  0x01
#define AFR_BAUDOUT_SEL 0x02
#define AFR_RXRDY_SEL   0x04

/* ISR bits */
#define INT_STATUS(r)   ((r)&1)
#define INT_PRIORITY(r) (((r)>>1)&0x7)

/* LCR bits */
#define WORD_LENGTH(n)  (((n)-5)&0x3)
#define STOP_BIT_ENABLE 0x04
#define PARITY_ENABLE   0x08
#define EVEN_PARITY     0x10
#define FORCE_PARITY    0x20
#define XMIT_BREAK      0x40
#define DLAB_ENABLE     0x80

/* MCR bits */
#define _DTR 0x01
#define _RTS 0x02
#define _OP1 0x04
#define _OP2 0x08
#define LOOP_BACK 0x10

/* LSR Bits */
#define RCVR_DATA_READY 0x01
#define OVERRUN_ERROR   0x02
#define PARITY_ERROR    0x04
#define FRAMING_ERROR   0x08
#define BREAK_INTERRUPT 0x10
#define XMIT_HOLD_EMPTY 0x20
#define XMIT_EMPTY      0x40
#define FIFO_ERROR      0x80
#define RCVR_READY(u)   (_LSR(u)&RCVR_DATA_READY)
#define XMIT_READY(u)   (_LSR(u)&XMIT_HOLD_EMPTY)

/* MSR bits */
#define _RDR       0x01
#define DELTA_DSR  0x02
#define DELTA_RI   0x04
#define DELTA_CD   0x08
#define _CTS       0x10
#define _DSR       0x20
#define _RI        0x40
#define _CD        0x80


/* Compute 16-bit divisor for baudrate generator, with rounding:  */
#define UART_DIVISOR(clock,baud)    (((clock)/16 + (baud)/2)/(baud))

/* Prototypes of driver functions */
extern void     uart16550_init( uart_dev_t *u, unsigned baud, unsigned ndata,
                                unsigned parity, unsigned nstop );
extern void     uart16550_out( uart_dev_t *u, char c );
extern char     uart16550_in( uart_dev_t *u );
extern unsigned uart16550_measure_sys_clk( uart_dev_t *u );

#endif /* _UART_16550_H_ */