Datasheet

1 .program auto_push_pull
2
3 .wrap_target
4 out x, 32
5 in x, 32
6 .wrap
Ê1 #include "tb.h" // TODO this is built against existing sw tree, so that we get printf etc
Ê2
Ê3 #include "platform.h"
Ê4 #include "pio_regs.h"
Ê5 #include "system.h"
Ê6 #include "hardware.h"
Ê7
Ê8 #include "auto_push_pull.pio.h"
Ê9
10 int main()
11 {
12 tb_init();
13
14 // Load program and configure state machine 0 for autopush/pull with
15 // threshold of 32, and wrapping on program boundary. A threshold of 32 is
16 // encoded by a register value of 00000.
17 for (int i = 0; i < count_of(auto_push_pull_program); ++i)
18 mm_pio->instr_mem[i] = auto_push_pull_program[i];
19 mm_pio->sm[0].shiftctrl =
20 (1u << PIO_SM0_SHIFTCTRL_AUTOPUSH_LSB) |
21 (1u << PIO_SM0_SHIFTCTRL_AUTOPULL_LSB) |
22 (0u << PIO_SM0_SHIFTCTRL_PUSH_THRESH_LSB) |
23 (0u << PIO_SM0_SHIFTCTRL_PULL_THRESH_LSB);
24 mm_pio->sm[0].execctrl =
25 (auto_push_pull_wrap_target << PIO_SM0_EXECCTRL_WRAP_BOTTOM_LSB) |
26 (auto_push_pull_wrap << PIO_SM0_EXECCTRL_WRAP_TOP_LSB);
27
28 // Start state machine 0
29 hw_set_bits(&mm_pio->ctrl, 1u << (PIO_CTRL_SM_ENABLE_LSB + 0));
30
31 // Push data into TX FIFO, and pop from RX FIFO
32 for (int i = 0; i < 5; ++i)
33 mm_pio->txf[0] = i;
34 for (int i = 0; i < 5; ++i)
35 printf("%d\n", mm_pio->rxf[0]);
36
37 return 0;
38 }
Figure 44 shows how the state machine executes the example program. Initially the OSR is empty, so the state machine
stalls on the first OUT instruction. Once data is available in the TX FIFO, the state machine transfers this into the OSR. On
the next cycle, the OUT can execute using the data in the OSR (in this case, transferring this data to the X scratch
register), and the state machine simultaneously refills the OSR with fresh data from the FIFO. Since every IN instruction
immediately fills the ISR, the ISR remains empty, and IN transfers data directly from scratch X to the RX FIFO.
RP2040 Datasheet
3.5. Functional Details 356