diff options
Diffstat (limited to 'arch/x86/lib/pcat_timer.c')
| -rw-r--r-- | arch/x86/lib/pcat_timer.c | 10 |
1 files changed, 5 insertions, 5 deletions
diff --git a/arch/x86/lib/pcat_timer.c b/arch/x86/lib/pcat_timer.c index 3545a50..ce15818 100644 --- a/arch/x86/lib/pcat_timer.c +++ b/arch/x86/lib/pcat_timer.c @@ -9,17 +9,17 @@ #include <asm/io.h> #include <asm/i8254.h> -#define TIMER2_VALUE 0x0a8e /* 440Hz */ +#define TIMER2_VALUE 0x0a8e /* 440Hz */ int pcat_timer_init(void) { /* - * initialize 2, used to drive the speaker - * (to start a beep: write 3 to port 0x61, - * to stop it again: write 0) + * Initialize counter 2, used to drive the speaker. + * To start a beep, set both bit0 and bit1 of port 0x61. + * To stop it, clear both bit0 and bit1 of port 0x61. */ outb(PIT_CMD_CTR2 | PIT_CMD_BOTH | PIT_CMD_MODE3, - PIT_BASE + PIT_COMMAND); + PIT_BASE + PIT_COMMAND); outb(TIMER2_VALUE & 0xff, PIT_BASE + PIT_T2); outb(TIMER2_VALUE >> 8, PIT_BASE + PIT_T2); |