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| author | Daniel Friesel <derf@finalrewind.org> | 2013-10-06 19:37:45 +0200 |
|---|---|---|
| committer | Daniel Friesel <derf@finalrewind.org> | 2013-10-06 19:37:45 +0200 |
| commit | aec0c5fd369fdf9cdbf3609b7559abf146f5ac42 (patch) | |
| tree | 737991b4f524150cb9c6cb7a90fa12528e77dd49 | |
| parent | 0189b7cfe970b88aeb1a4fb2aa328eeee42079a8 (diff) | |
increased timing precision, more robust code
| -rw-r--r-- | read-rom/Makefile | 4 | ||||
| -rw-r--r-- | read-rom/main.c | 57 |
2 files changed, 41 insertions, 20 deletions
diff --git a/read-rom/Makefile b/read-rom/Makefile index 0b9e15c..c31d4ec 100644 --- a/read-rom/Makefile +++ b/read-rom/Makefile @@ -9,8 +9,10 @@ AVROBJDUMP ?= avr-objdump CFLAGS += -mmcu=attiny2313 -DF_CPU=20000000UL #CFLAGS += -gdwarf-2 -fverbose-asm -save-temps -CFLAGS += -I. -std=gnu99 -O2 -Wall -Wextra -pedantic +CFLAGS += -I. -std=gnu99 -Os -Wall -Wextra -pedantic CFLAGS += -funsigned-char -funsigned-bitfields -fpack-struct -fshort-enums +# r28 .. r31 hold the microsecond counters +CFLAGS += -ffixed-28 -ffixed-29 -ffixed-30 -ffixed-31 CFLAGS += -fwhole-program -flto -mstrict-X AVRFLAGS += -U lfuse:w:0xe4:m -U hfuse:w:0xdf:m -U efuse:w:0xff:m diff --git a/read-rom/main.c b/read-rom/main.c index e20b45f..9c0d3ba 100644 --- a/read-rom/main.c +++ b/read-rom/main.c @@ -63,32 +63,46 @@ int main (void) asm volatile ("ldi r30, 0"); asm volatile ("ldi r31, 0"); - // 1us - while (1) { // 1c - asm volatile ("inc r30"); // 1c - asm volatile ("adiw r28, 1"); // 2c - asm volatile ("wdr"); // 1c - } + // 1us per cycle +loop: + asm volatile ("inc r30"); // 1c + asm volatile ("adiw r28, 1"); // 2c + asm volatile ("wdr"); // 1c + asm volatile ("nop"); // 1c + asm volatile ("nop"); // 1c + asm volatile ("nop"); // 1c + goto loop; return 0; } ISR(INT1_vect) { + // overhead: 19c (2.4us) if (PIND & _BV(PD3)) { - asm("out 0x15, r29"); // LCNTH - asm("out 0x14, r28"); // LCNTL - asm("out 0x13, r30"); // HCNTL + asm volatile ("out 0x15, r29"); // LCNTH + asm volatile ("out 0x14, r28"); // LCNTL + asm volatile ("out 0x13, r30"); // HCNTL // > 256us - reset if (LCNTH > 0) { DDRD = _BV(PD3); - // 120us - for (CNT = 0; CNT < 120; CNT++) { - asm volatile ("wdr"); - } + + // 120us loop - r31 / r30 need not be preserved + asm volatile ("ldi r31, 0"); + asm volatile ("ldi r30, 120"); // Z = 120 + asm volatile ("wdr"); // <----- + asm volatile ("wdr"); + asm volatile ("wdr"); + asm volatile ("sbiw r30, 1"); + asm volatile ("cp r30, r1"); + asm volatile ("brne .-12"); // -^ + DDRD = 0; + LASTCMD = 0; + BUF = 0; + POS = 0; asm volatile ("wdr"); EIFR |= _BV(INTF1); } @@ -109,7 +123,6 @@ ISR(INT1_vect) POS = 1; APOS = 0; BYTE = ~ADDR8; - MCUCR = _BV(ISC11); EIFR |= _BV(INTF1); } @@ -122,10 +135,17 @@ ISR(INT1_vect) if (BYTE & POS) { DDRD = _BV(PD3); - // 15us - for (CNT = 0; CNT < 18; CNT++) { - asm volatile ("wdr"); - } + + // 15us loop - r31 / r30 need not be preserved + asm volatile ("ldi r31, 0"); + asm volatile ("ldi r30, 15"); // Z = 120 + asm volatile ("wdr"); // <----- + asm volatile ("wdr"); + asm volatile ("wdr"); + asm volatile ("sbiw r30, 1"); + asm volatile ("cp r30, r1"); + asm volatile ("brne .-12"); // -^ + DDRD = 0; asm volatile ("wdr"); EIFR |= _BV(INTF1); @@ -153,7 +173,6 @@ ISR(INT1_vect) else if (APOS == 8) { LASTCMD = 0; - MCUCR = _BV(ISC10); POS = 0; } } |