uart.asm

这是在C5000系列DSP上实现UART（异步串口）TL16c550芯片的汇编语言实现代码

*********************************************************************************
* UART program , communicating with PC
* WRITED BY Baiyangong    
* DATA: 4/6/2004 
*********************************************************************************
			.mmregs
			.global _main
			.global UART_INT
	
_main:
            ;UART regs address start at 0x4000
*********************************************************************************
;Register Selection Table
;-------------------------------------------------------------------------------------
;  DLAB  | A2 | A1 | A0 |                         Registers                           |
;    0   | 0  | 0  | 0  | Rceciver Buffer(Read) , Transmitter holding register(write) |
;    0   | 0  | 0  | 1  | Interrupt enable register                                   |
;    x   | 0  | 1  | 0  | Interrupt Identification register(Read only)                |
;    x   | 0  | 1  | 0  | FIFO control register (write)                               |
;    x   | 0  | 1  | 1  | Line Control register                                       |
;    x   | 1  | 0  | 0  | Modem control register                                      |
;    x   | 1  | 0  | 1  | Line sratus register                                        |
;    x   | 1  | 1  | 0  | Modem status register                                       |
;    x   | 1  | 1  | 1  | Scratch register                                            |
;    1   | 0  | 0  | 0  | Divisor latch(LSB)                                          |
;    1   | 0  | 0  | 1  | Divesor latch(MSB)                                          |
*-------------------------------------------------------------------------------------  
            ;DLAB is the MSB of LCR , before initiation 550 ,must set DLAB to setup DIVISION
            ;so the access DLAB address is 0x4003
            ;the A0->A2 can access the UART
            
**********************************************************************************
            .include "subfunction.inc"
					;define macro
		    .include "subfunction2.inc"
					;define macro
            .include "init_5410.inc"
					;define the initial value of cpu and peripheral registers
            .include "TL16C550C.inc"
                     ;Definition of TL16C550C
            .include "Address_peripheral.inc"
					;define the peripheral address         
            
            .text
;=============================================================
;           system initiation
;=============================================================
           INIT_CPU
           INIT_PERIPHERAL
;=============================================================
;           UART initiation
;=============================================================                                                
            STM #TL_IER , AR1
            PORTW AR1 , IER
            NOP
            NOP
            NOP
            NOP
                     ;IER init
            STM #TL_FCR , AR1
            PORTW AR1 , FCR
            NOP
            NOP
            NOP
            NOP
                     ;FCR init
            STM #0x0080 , AR1 
            PORTW AR1 , LCR
            NOP
            NOP
            NOP
            NOP                     
           
            STM #0x0018 , AR1
            PORTW AR1 , DLSB
            NOP
            NOP
            NOP
            NOP
                     ;set Division MSB
                      
            STM #0x0000 , AR1
            PORTW AR1 , DMSB
            NOP
            NOP
            NOP
            NOP
                     ;set Division LSB                           
            STM #TL_LCR , AR1
            PORTW AR1 , LCR
            NOP
            NOP
            NOP
            NOP
                     ;LCR init
            ;B loop                    
            RSBX INTM
                      
end:        BD end
            NOP
            NOP
            
UART_INT:
            PORTR IIR , AR1
            ANDM #0x000F , AR1  ;obtain the A[3..0]
            ;CASE  A[3..0]=0110b  Line Status interrupt
            ;CASE         =0100b  Data available interrupt
            ;CASE         =1100b  time_out interrupt (FIF0 MODE)
            ;CASE         =0010b  transmitter holding register empty interrupt
            ;CASE         =0000b  Modem status interrupt
            CMPM AR1 , #0x0006
            CC Line_Status_int , TC
            NOP
            NOP
            CMPM AR1 , #0x0004
            CC Data_available_int , TC
            NOP
            NOP
            CMPM AR1 , #0x000C
            CC time_out_int , TC  
            NOP
            NOP
            CMPM AR1 , #0x0002 
            CC trans_hold_register_empty , TC
            NOP
            NOP
            CMPM AR1 , #0x0000
            CC Modem_status_int , TC
            NOP
            NOP
            NOP
            BD done    ;default 
            NOP
            NOP
            
Line_Status_int:
            PORTR LSR , AR2
            BD done
            NOP
            NOP
                        
Data_available_int:
            PORTR RBR , AR2 
            BD done
            NOP
            NOP

time_out_int:
            PORTR RBR , AR2
            BD done
            NOP
            NOP
            
trans_hold_register_empty:
            STM #0x00AA , AR0     
            PORTW AR0 , THR
            BD done
            NOP
            NOP
                   
Modem_status_int:
            PORTR MSR , AR2
            BD done
            NOP
            NOP
         
done:
            RSBX TC  ; TC=0
            RETE
            NOP
            NOP
            
            .end