3 .word ( 0x0260 | 1<<0 | 5<<2 | 1<<7 | 3<<10 )
4 ; reserved_bits | security_off | lvr_1v8 | io_drv_norm | boot_fast
7 notes: .ds 16 ; 0x00 .. 0x0f
14 .even ; make next two bytes word-aligned
18 .even ; SP must be aligned
23 ; aliases for memory locations:
48 ; Calibration Parameters:
49 ; Bitshift Variations calls for an 8kHz sample rate; with an interrupt every
50 ; 512 cycles (the next power of two above the 495 cycles the program needs for
51 ; execution), this gives us a clock speed of 512 * 8khz = 4.096MHz. The MCU
52 ; will be powered by a 3V lithium coin cell.
54 calib_freq = 4096000 ; Hz
58 ; during playback: IHRC/4, WDT off, keep ILRC on
59 active_clock = (( 0<<5 | 1<<4 | 0<<3 | 1<<2 | 0<<1 | 0<<0 ))
60 ; during deep-sleep: ILRC/1, WDT off
61 sleep_clock = (( 7<<5 | 1<<4 | 0<<3 | 1<<2 | 0<<1 | 0<<0 ))
62 ; for extra power saving, consider: 6<<5|0<<3 for ilrc/4, 2<<5|1<<3 for ilrc/16
64 ; cycle count (worst-case)
67 ; sample: 115 + 4*g + 2*mod3 = 495
69 ; TOTAL: sample + overhead = 507
82 .org 0x0040 ; leave some space after IVT to allow 'overprogramming'
85 ADD mod3lo, a ; mod3lo = hi+lo
93 AND a, #0xf ; (mod3lo>>4)
94 XCH mod3lo ; a=mod3lo, mod3lo=mod3lo>>4
95 AND a, #0xF ; a=mod3lo&0xf, mod3lo=mod3lo>>4
96 ADD a, mod3lo ; (mod3lo & 0xF)
100 AND a, #0x3 ; a = (mod3lo & 0x3)
102 SR mod3lo ; (mod3lo >> 2)
106 AND a, #0x3 ; a = (mod3lo & 0x3)
108 SR mod3lo ; (mod3lo >> 2)
117 CLEAR mul2 ; this is notes_ix_hi (and should be 0)
119 MOV notes_ix, a ; assumes notes are the first thing in SRAM
128 CLEAR mul1 ; alias of notes_ix, so clear after idxm
129 ; note: LSB of result (mul0) is not needed for our purposes
204 SET1 clkmd, #4 ; enable IHRC
206 MOV clkmd, a ; switch to IHRC
208 ; calibration placeholder:
213 AND a, #( calib_freq )
214 AND a, #( calib_freq>>8 )
215 AND a, #( calib_freq>>16 )
216 AND a, #( calib_freq>>24 )
217 AND a, #( calib_vdd )
218 AND a, #( calib_vdd>>8 )
221 .word 0xffff, 0xffff, 0xffff, 0xffff, 0xffff
222 .word 0xffff, 0xffff, 0xffff, 0xffff, 0xffff
230 MOV a, #0x50 ; data direction: PWM & debug output, rest input
231 MOV pac, a ; (conserves power, apparently)
233 MOV padier, a ; disable pin wakeup, except on audio pin
234 MOV paph, a ; enable pull-up on audio pin
235 ; Line input typically has an impedance of 10k-100kOhm, so we need our
236 ; pull-ups to be even higher. Since the ones of the PMS150C are
237 ; typically 100k-220k, we can use it and don't need an external one.
239 MOV pa, a ; PortA data = 0
242 ; Since (unlike in the ATTiny4 version) the interrupt timer is not tied
243 ; to the PWM frequency, we can use a much faster clock for PWM. The
244 ; highest "carrier frequency" for the PCM samples we can generate is by
245 ; setting Timer2 to 6 bit, (IHRC/1)/1 mode, giving a frequency of
246 ; (4*4.096MHz)/2^6 = 256kHz. We really use (4*4.096MHz)/2^8 = 64kHz.
249 MOV a, #(( 2<<4 | 3<<2 | 1<<1 | 0<<0 ))
250 MOV tm2c, a ; timer2: IHRC, PA4, PWM, not inverted
251 MOV a, #(( 0<<7 | 0<<5 | 0<<0 ))
252 MOV tm2s, a ; 8bit, /4 prescaler, divide by (0+1)
255 MOV a, #(( 0<<0 | 1<<3 | 4<<5 )) ; ovf@bit8 (512cy; ยง9.2.5), clk/4, ihrc
256 ;^xxx: could use 0b000000 syntax for compact binary values
258 MOV a, #(1<<2) ; enable timer16 int, disable all others
262 SET1 eoscr, #0 ; disable bandgap and lvr
263 SET0 gpcc, #7 ; disable comparator
270 ;rom is not mmapped; must load notes into ram first
299 CEQSN a, #0x78 ; compare, skip next if equal
300 ; Note: usually, this is the place where the MCU is put into some
301 ; sort of low power/sleep mode. But the Padauk's stopexe instruction
302 ; causes the ISR to a) run at greatly reduced frequency (100hz vs
303 ; 1khz for timer16@bit11; probably due to slow wakeup), b)
304 ; double-fire some (20-30%) of the time, c) jitter -50% to +10%. so
305 ; we don't sleep at all between samples (which is only a short time
309 ; at this point, i2==0x78, i.e. the music is finished.
310 ; => goto halt (fallthrough)
313 CLEAR i2 ; clear halting signal
315 ; Note: disabling the timers isn't strictly necessary (as stopsys halts
316 ; all timers anyways), but I'm hoping it may reduce power consumption.
317 ; We're lucky that we only need to toggle a single bit to switch
318 ; between the required clock source and 'off' (0010xxxx->0000xxxx for
319 ; timer2, 100xxxxx->000xxxxx for timer16), so we can hack our way out
320 ; of loading an immediate each time.
324 SET1 pa, #4 ; assert a high level on the audio pin for good measure
325 SET0 pac, #4 ; ... before setting it to input mode (optional)
327 ;switch to ilrc clock
330 SET0 clkmd, #4 ; disable ihrc
333 ; (at this point, we wait for an i/o-toggle wake up event to resume execution)
336 MOV clkmd, a ; switch to IHRC again
338 SET1 pac, #4 ; restore output mode for audio pin
340 ;reenable timer16, timer2
349 T1SN intrq, #2 ; if intrq.t16 is triggered, skip next
357 ; send pwm data to timer2:
361 ; generate new sample:
363 MOV a, i2; "mov mem,mem"
364 MOV n, a; does not exist
385 MOV tmp_1, a ; fresh tmp_1:
390 OR a, tmp_1 ; tmp_1 done.
419 MOV tmp_1, a ; a saved in tmp_1; fresh a
421 ; shift-divide by six
422 ; note: i2 is max 0x78; so a will <= 20. (breaks for values >=128)
435 AND a, tmp_1 ; a restored from tmp_1
459 MOV tmp_1, a ; a saved in tmp_1; fresh a
461 ; shift-divide by ten
462 ; note: i2 is max 0x78; so a will <= 12.
475 AND a, tmp_1 ; a restored from tmp_1
482 ; next sample is now ready.