/*
 * sleep — block for N seconds using the 50 Hz frame interrupt.
 *
 * Sprinter ISR fires 50 times per second.  `halt` parks the CPU until
 * the next IRQ, so 50 halts = ~1 second of wall clock.  This is the
 * same trick solid-c uses in IO.ASM:285.
 *
 * Note: requires interrupts to be enabled (they are by default — ESTEX
 * sets up IM 1 with the frame ISR before our program runs).
 */

#include <unistd.h>

void sleep(unsigned int seconds) __naked
{
    (void)seconds;
    __asm
    inter:
        ;; HL = seconds on entry (SDCC single int arg).
        ld    a, h
        or    a, l
        ret   Z                     ; sleep(0) — return immediately
        ld    b, #50                ; 50 halts per second (50 Hz interrupt)
    inner:
        halt
        djnz  inner
        dec   hl
        jr    inter
    __endasm;
}