auto_baud.asm

bf533平台图像采集程序

#include <defBF533.h>
.section L1_code;
.global _uart_autobaud;
_uart_autobaud:

	[--sp] = r2;
	[--sp] = p1;

/*****************************************************************************
 *
 *  First of all, enable UART clock. It is required for autobaud detection on 
 *  silicon revision 0.0.
 *
 ****************************************************************************/ 
	
 	p0.l = lo(UART_GCTL);
	p0.h = hi(UART_GCTL);	
	r0 = UCEN (z);
	w[p0+UART_GCTL-UART_GCTL] = r0;
	

/*****************************************************************************
 *
 *  Activate Loopback mode in order the receive channel is disconnected 
 *  from RX pin during autobaud detection.
 *
 ****************************************************************************/ 

 	r0 = LOOP_ENA (z);
	w[p0+UART_MCR-UART_GCTL] = r0;	
		
			
/*****************************************************************************
 *
 *  Setup Timer 2 Controller to do the autobaud detection. Timer captures
 *  duration between two falling edges. It expects a '@' (ASCII 0x40) 
 *  character. 8-bit, no parity assumed.
 *
 ****************************************************************************/ 

	p1.h = hi(TIMER_STATUS);
	p1.l = lo(TIMER_STATUS);

		
/*****************************************************************************
 *
 *  Disable Timer 2 first, in case there was an unexpected history.  
 *
 ****************************************************************************/ 

	r0 = TIMDIS2 (z);
	w[p1 + TIMER_DISABLE - TIMER_STATUS] = r0;
	
	r0 = TRUN2 | TOVL_ERR2 | TIMIL2 (z);
	w[p1 + TIMER_STATUS - TIMER_STATUS] = r0;

	 
/*****************************************************************************
 *
 *  Capture from UART RxD pin. Select period capture from falling edge to 
 *  falling edge. Enable IRQ_ENA, but don't enable the interrupt at system 
 *  level (SIC). 
 *
 ****************************************************************************/ 
 		
 	r0 = TIN_SEL | IRQ_ENA | PERIOD_CNT | WDTH_CAP (z);				
	w[p1 + TIMER2_CONFIG - TIMER_STATUS] = r0;	

	
/*****************************************************************************
 *
 *  Start the timer and wait until the according interrupt latch bit TIMIL2
 *  in the TIMER_STATUS register is set. Then, two falling edges on the RxD
 *  pin have been detected.
 *
 ****************************************************************************/ 
	
	r0 =  TIMEN2 (z);
	w[p1 + TIMER_ENABLE - TIMER_STATUS] = r0;	
	
wait_autobaud:
	r0 = w[p1 + TIMER_STATUS - TIMER_STATUS] (z);
	CC = bittst (r0, bitpos (TIMIL2) );
	if !CC jump wait_autobaud;
	

/*****************************************************************************
 *
 *  Disable Timer 2 again  
 *
 ****************************************************************************/ 

 	r0 = TIMDIS2 (z);
	w[p1 + TIMER_DISABLE - TIMER_STATUS] = r0;

	r0 = TRUN2 | TOVL_ERR2 | TIMIL2 (z);
	w[p1 + TIMER_STATUS - TIMER_STATUS] = r0;
	
	 			
/*****************************************************************************
 *
 *  Save period value to R2
 *
 ****************************************************************************/ 

 	r2 = [p1 + TIMER2_PERIOD - TIMER_STATUS]; 
 
 		
/*****************************************************************************
 *
 *  In order to support also half-duplex connections, we need to delay any 
 *  transmission, in order the sent character does not overlap the autobaud
 *  pattern.
 *
 *  Use Timer 2 to perform this delay. Note that the Period Register still
 *  contains the proper value and the Width Register is not used.
 *
 ****************************************************************************/	
	
 	r0 = OUT_DIS | IRQ_ENA | PERIOD_CNT | PWM_OUT (z);				
	w[p1 + TIMER2_CONFIG - TIMER_STATUS] = r0;	
	
	r0 =  TIMEN2 (z);
	w[p1 + TIMER_ENABLE - TIMER_STATUS] = r0;	
	
wait_delay:
	r0 = w[p1 + TIMER_STATUS - TIMER_STATUS] (z);
	CC = bittst (r0, bitpos (TIMIL2) );
	if !CC jump wait_delay;

/*****************************************************************************
 *
 *  Disable Timer 2 again  
 *
 ****************************************************************************/ 

 	r0 = TIMDIS2 (z);
	w[p1 + TIMER_DISABLE - TIMER_STATUS] = r0;

	r0 = TRUN2 | TOVL_ERR2 | TIMIL2 (z);
	w[p1 + TIMER_STATUS - TIMER_STATUS] = r0;	
		
	
/*****************************************************************************
 *
 *  Deactive Loopback mode again
 *
 ****************************************************************************/ 	
		
	r0 = 0 (z);
	w[p0+UART_MCR-UART_GCTL] = r0;	

	
/*****************************************************************************
 *
 *  done !
 *
 ****************************************************************************/ 	
	r0 = r2;
 /*****************************************************************************
 *
 *  r0 holds the timer period value, now.
 *  Apply formula DL = PERIOD / (16 x 8 bits) and call uart_init that writes
 *  the result to the two 8-bit DL registers (DLH:DLL).
 *
 ****************************************************************************/ 
		
 	
 	
 	r0 >>= 7;
	p1 = [sp++];
	r2 = [sp++];		
	
	rts;

_uart_autobaud.end: