4510下的UART的问题
大家帮帮忙，我在4510下写了一个用UART口来实现printf的功能的函数，可是不知道为什么总是在红色的那一行上循环，总是检测不到可写状态。我看了半天4510的手册，可是还是没有搞懂。望大家指点。下面是代码/*
* Serial settings.......................
*/
#ifndef SYSCFG
#define SYSCFG 0x03FF0000
#endif
#define UART0_BASE (SYSCFG + 0xD000)
/* add 19200 for test uue */
#define BAUD_19200 (80 << 4)
#define ULCON 0x00
#define UCON 0x04
#define USTAT 0x08
#define UTXBUF 0x0C
#define URXBUF 0x10
#define UBRDIV 0x14
/*
* Line control register bits............
*/
#define ULCR8bits (3)
/*
* UART Control Register bits............
*/
#defineUCRRxM (1)
#defineUCRRxSI (1 << 2)
#defineUCRTxM (1 << 3)
#defineUCRLPB (1 << 7)
/*
* UART Status Register bits
*/
#define USRTxHoldEmpty(1 << 6)
#define USRTxEmpty (1 << 7)
// UART registers are on word aligned, D8
/* UART primitives */
#define GET_STATUS(p)(*(volatile unsigned*)((p) + USTAT))
#define RX_DATA(s) ((s) & USRRxData)
#define GET_CHAR(p) (*(volatile unsigned*)((p) + URXBUF))
#define TX_READY(s) ((s) & USRTxHoldEmpty)
#define PUT_CHAR(p,c) (*(unsigned*)((p) + UTXBUF) = (unsigned )(c))
void uart_init( unsigned int UART_BASE, unsigned int baud )
{
/* Disable interrupts*/
*(volatile unsigned *) (UART_BASE + UCON) = 0;
/* Set port for 8 bit, one stop, no parity*/
*(volatile unsigned *) (UART_BASE + ULCON) = (ULCR8bits);
/* Enable interrupt operation on UART */
*(volatile unsigned *) (UART_BASE + UCON) = UCRRxM | UCRTxM;
/* Set baud rate*/
*(volatile unsigned *) (UART_BASE + UBRDIV) = baud;
}
int uart_putchar( unsigned int UART_BASE, char ch )
{
/* read tx ready flag, when =1 break */
while(TX_READY( GET_STATUS( UART_BASE ) ) ==0 )；
PUT_CHAR(UART_BASE, ch);
return ch;
}
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