====== 7. Vstupně výstupní subsystém - 1. část ======

{{.:lekce07-io.pdf|PDF}}

[[https://gitlab.fel.cvut.cz/b35apo/apo-slides/-/tree/main/07-io|TeX]]

=== Další materiály ===
{{..:..:en:lectures:07:b35apo_lecture07-io-1.pdf|Input/Output Subsystem - Part 1}}

{{..:..:en:lectures:07:b35apo_lecture07-io-1.odp|ODP}}

=== Programové ukázky ===

Program na výpis řetězce na sériový port pro QtRvSim
<code>
.equ SERIAL_PORT_BASE,   0xffffc000 
#base address of QtRVSim serial port

.equ SERP_RX_ST_REG,       0xffffc000  #Receiver status register
.equ SERP_RX_ST_REG_o,     0x0000      #Offset of RX_ST_REG
.equ SERP_RX_ST_REG_READY_m, 0x1 #Data byte is ready to be read
.equ SERP_RX_ST_REG_IE_m,    0x2 #Enable Rx ready interrupt

.equ SERP_RX_DATA_REG,   0xffffc004 #Received data byte in 8 LSB bits
.equ SERP_RX_DATA_REG_o,   0x0004   #Offset of RX_DATA_REG

.equ SERP_TX_ST_REG,     0xffffc008 #Transmitter status register
.equ SERP_TX_ST_REG_o,     0x0008   #Offset of TX_ST_REG
.equ SERP_TX_ST_REG_READY_m,  0x1 #Transmitter can accept next byte
.equ SERP_TX_ST_REG_IE_m,     0x2 #Enable Tx ready interrupt

.equ SERP_TX_DATA_REG,   0xffffc00c #Write word to send 8 LSB bits
.equ SERP_TX_DATA_REG_o,   0x000c   #Offset of TX_DATA_REG

write:
    li   a0, SERIAL_PORT_BASE # a0 ukazuje na zacatek pameti UART
    la   a1, text_1           # nacti ukazatel na retezec
next_char:
    lb   t1, 0(a1)            # nacti znak k odeslani
    beq  t1, zero, end_char   # 0 ukoncuje retezec
    addi a1, a1, 1            # posun ukazatel
tx_busy:
    lw   t0, SERP_TX_ST_REG_o(a0)       # zjisti statu odesilaci fronty
    andi t0, t0, SERP_TX_ST_REG_READY_m # vymaskuj bit READY
    beq  t0, zero, tx_busy    # pokud neni volno v UARTU cekej zkus to znovu
    sw   t1, SERP_TX_DATA_REG_o(a0) # je volno - zapis bajt
    j    next_char            # posli dalsi znak
end_char:
    ebreak                    # ukonci program

    .data
text_1:
    .asciz  "Hello world.\n"  # retezec ukonceny 0
</code>

Program čtení ze sériového portu pro QtRvSim
<code>
.equ SERIAL_PORT_BASE,   0xffffc000 
#base address of QtRVSim serial port

.equ SERP_RX_ST_REG,       0xffffc000  #Receiver status register
.equ SERP_RX_ST_REG_o,     0x0000      #Offset of RX_ST_REG
.equ SERP_RX_ST_REG_READY_m, 0x1 #Data byte is ready to be read
.equ SERP_RX_ST_REG_IE_m,    0x2 #Enable Rx ready interrupt

.equ SERP_RX_DATA_REG,   0xffffc004 #Received data byte in 8 LSB bits
.equ SERP_RX_DATA_REG_o,   0x0004   #Offset of RX_DATA_REG

.equ SERP_TX_ST_REG,     0xffffc008 #Transmitter status register
.equ SERP_TX_ST_REG_o,     0x0008   #Offset of TX_ST_REG
.equ SERP_TX_ST_REG_READY_m,  0x1 #Transmitter can accept next byte
.equ SERP_TX_ST_REG_IE_m,     0x2 #Enable Tx ready interrupt

.equ SERP_TX_DATA_REG,   0xffffc00c #Write word to send 8 LSB bits
.equ SERP_TX_DATA_REG_o,   0x000c   #Offset of TX_DATA_REG

gets: 
    li   a0, SERIAL_PORT_BASE # a0 ukazuje na zacatek pameti UART
    la   a1, text_1           # nacti ukazatel na buffer
    addi t2, zero, 40
next_char:
rx_not_ready:
    lw   t0, SERP_RX_ST_REG_o(a0)       # zjisti statu prijimaci fronty
    andi t0, t0, SERP_RX_ST_REG_READY_m # vymaskuj bit READY
    beq  t0, zero, rx_not_ready    # pokud neni znak UARTU cekej zkus to znovu
    lw   t1, SERP_RX_DATA_REG_o(a0) # je znak - precti ho a tim odstran
    sb   t1, 0(a1)            # uloz znak do bufferu
    addi t1, t1, -13          # test je to novy radek?
    beq  t1, zero, end_char   # ukoncuje cteni
    addi a1, a1, 1            # posun ukazatel
    addi t2, t2, -1            # kontroluj kolik muzeme nacist
    bne  t2, zero, next_char
end_char:
    ebreak                    # ukonci program
    .data
text_1:
    .word 0,0,0,0,0,0,0,0,0,0
</code>

Program pro práci s otočnými voliči v QtRvSim
<code>
#base of SPILED port region
.equ SPILED_REG_BASE,       0xffffc100

#RGB LED 1 barevne slozky – 8 bitu kazda
.equ SPILED_REG_LED_RGB1,   0xffffc110
.equ SPILED_REG_LED_RGB1_o,   0x0010

#RGB LED 2 barevne slozky – 8 bitu kazda
.equ SPILED_REG_LED_RGB2,   0xffffc114
.equ SPILED_REG_LED_RGB2_o,   0x0014

#Tri 8 bitove otocne volice
#nejvyssi bajt informace o stitsknuti
.equ SPILED_REG_KNOBS_8BIT, 0xffffc124 
.equ SPILED_REG_KNOBS_8BIT_o, 0x0024

#32 LEDek kazdy bit jedna LED dioda
.equ SPILED_REG_LED_LINE,   0xffffc104
.equ SPILED_REG_LED_LINE_o,   0x0004

    li   a0, SPILED_REG_BASE # a0 ukazuje na zacatek pameti pro I/O
    ori  t2, t2, -1
loop:
    lw   t0, SPILED_REG_KNOBS_8BIT_o(a0)   # nacti data od otocnych volicu
    sw   t0, SPILED_REG_LED_RGB1_o(a0)
    xor  t1, t0, t2
    sw   t1, SPILED_REG_LED_RGB2_o(a0)
    srli t0, t0, 24
    andi t0, t0, 4
    beq  t0, zero, loop    # pokud nebyl zmacknut cerveny volic

    ebreak                    # ukonci program
</code>

{{:courses:b35apo:lectures:07:signal_speed.gif?600| Vliv frekvence na paralelní sběrnici}}

{{ :courses:b35apo:lectures:07:signal_speed.mp4 | Vliv frekvence na paralelní sběrnici}}