Please complete the char_out and char_in functions in this assembly code.

When writing the char_out and char_in routines, only use registers R0 to R3 and R12 as using any other registers requires the values to be saved and restored in the function. The char_out and char_in routines should implement the logic shown in Figure 27 below. Note that the char_in routine needs to verify that the OR, NF, FE and PF bits are not set. If they are set, they can be cleared by writing a one to the specific bit location or by simply writing 0x0F to clear any that are set.

SIM_SOPT2 EQU 0x40048004

SIM_SCGC4 EQU 0x40048034 SIM_SCGC5 EQU 0x40048038

PORTA_PCR1 EQU 0x40049000 + 4 * 1 PORTA_PCR2 EQU 0x40049000 + 4 * 2

PORTE_PCR20 EQU 0x4004D000 + 4 * 20 PORTE_PCR21 EQU 0x4004D000 + 4 * 21

UART0_BDH EQU 0x4006A000 UART0_BDL EQU 0x4006A001 UART0_C1 EQU 0x4006A002 UART0_C2 EQU 0x4006A003 UART0_S1 EQU 0x4006A004 UART0_S2 EQU 0x4006A005 UART0_C3 EQU 0x4006A006 UART0_D EQU 0x4006A007 UART0_MA1 EQU 0x4006A008 UART0_MA2 EQU 0x4006A009 UART0_C4 EQU 0x4006A00A UART0_C5 EQU 0x4006A00B

AREA asm_area, CODE, READONLY EXPORT asm_main EXPORT UART0Init EXPORT char_in EXPORT char_out

asm_main FUNCTION ;assembly entry point for C function ; Add program code here

BL UART0Init loop BL char_in ; read char from UART, char in R0 BL char_out ; send char in R0 to UART b loop ENDFUNC

; When char_out is called, R0 contains ; the char to be sent out the UART char_out FUNCTION

BX LR ENDFUNC

; When char_in returns, R0 contains ; the char that was received char_in FUNCTION

BX LR ENDFUNC

UART0Init FUNCTION ; SIM_SOPT2[UART0SRC] = 01b (MCGFLLCLK or MCGPLLCLK/2 clock) ; and SIM_SOPT2[PLLFLLSEL] = 1b for MGCPLLCLK/2 LDR R0,=SIM_SOPT2 ;Load address of SIM_SOPT2 to R0 LDR R1,[R0] ;Put present value of SIM_SOPT2 into R1 LDR R2,=0xF3FEFFFF ;Load bits to clear ANDS R1,R2 ;AND values to clear bits LDR R2,=0x04010000 ;Load bits to set ORRS R1,R2 ;OR values to set bits STR R1,[R0] ;Put value back into SIM_SOPT2

; SIM_SCGC4[UART0] = 1 LDR R0,=SIM_SCGC4 LDR R1,[R0] LDR R2,=0x00000400 ORRS R1,R2 STR R1,[R0]

; SIM_SCGC5[PORTE thru A] = 1, turn on clock for all ports LDR R0,=SIM_SCGC5 ;Load address of SIM_SCGC5 to R0 LDR R1,[R0] ;Put value of SIM_SCGC5 into R1 LDR R2,=0x00003E00 ;Load value to turn on all port ;clocks into R2 ORRS R1,R2 ;OR R2 into R1 STR R1,[R0] ;Put value back into SIM_SCGC5

; PORTA_PCR1 , Clear ISF and set MUX = 2 LDR R0,=PORTA_PCR1 LDR R1,[R0] LDR R2,=0x01000200 ORRS R1,R2 STR R1,[R0]

; PORTA_PCR2 , Clear ISF and set MUX = 2 LDR R0,=PORTA_PCR2 LDR R1,[R0] LDR R2,=0x01000200 ORRS R1,R2 STR R1,[R0]

; UART0_C4[OSR]= 0x07 (for osr = x8) LDR R0,=UART0_C4 MOVS R1,#0x07 STRB R1,[R0]

; 9600 baud ; uart0_baud_clk = MGCPLLCLK/2 = 96MHz/2 = 48MHz ; SBR = uart0_baud_clk/(baud*osr) ; SBR = 48MHz/(9600 * 8) ; SBR = 625 = (0x0271)

; UART0_BDH = 0x02 LDR R0,=UART0_BDH MOVS R1,#0x02 STRB R1,[R0]

; UART0_BDL = 0x71 LDR R0,=UART0_BDL MOVS R1,#0x71 STRB R1,[R0]

; UART0_C2 = 0x02 (TE and RE = 1) LDR R0,=UART0_C2 MOVS R1,#0x0C STRB R1,[R0] BX LR ENDFUNC

; Put constants here

AREA data_area, DATA, READWRITE ; Put variables here

END

No char out char in (char in RO) Read Read UARTO S1 UARTO S1 Write 0x0F to UARTO S1 Yes Does OR or NF or FE or PFa 1 No No Does Does RDRF 1 TDRE 1 Yes Yes Write RO to Read UARTO D To RO UARTO D Return Return (char in RO) Figure 27 char out and char in diagrams