1 ;######################################################################
2 ; i2clib.inc - I2C LIBRARY - IMPLEMENTATION
4 ; See i2clib.asm for documentation of the interface to this file.
6 ; include /usr/share/gputils/header/p18f458.inc
8 ; include ../iwjpictest/insn-aliases.inc
10 ; include ../iwjpictest/clockvaries.inc
12 ; include morse+auto.inc
16 ;======================================================================
21 ; m_... routines used by master only
22 ; s_... routines used by slave only
23 ; <any other name> routines used by both
25 ; [ms]_event_... event handler, branched to from interrupt
26 ; handler; conditions are as in the name;
27 ; should `return' at end which will return
28 ; from i2c[ms]_interrupt
30 ; [sm]_event_bad[_...] event handler which panics; called when i2c
31 ; controller did something unexpected
33 ; m_improper_... panics; called when main program
34 ; does something wrong
36 ; [ms]_<anything else> routines or labels of some other kind
38 ; Whenever flow does not pass past the end of some code, we
39 ; have a boundary `;----------', and when flow passes past
40 ; an important label we sometimes mark it specially with `;...',
45 ; bt_f_if0 st, st_something
49 ; m_event_several_including_spong
50 ; bs_f st, st_sponging
51 ; bra metasyntacticing
56 ;============================================================
57 ; COMMON ADMINISTRATIVE ROUTINES and VARIABLES
61 sspstat res 1 ; master only
62 sspcon1 res 1 ; master only
63 sspcon2 res 1 ; master only
64 slave res 1 ; master only
65 slave_next res 1 ; master only
70 ; st is a bitmask, bit set in visible states:
72 st_starting equ 7 ; Writing-Setup?, Reading-Busy?
73 st_addressing equ 6 ; Writing-Setup?, Reading-Busy?
74 st_writing equ 5 ; Writing-*, Stopping(after Reading-Wait:write_start)
75 st_subsequent equ 4 ; Writing?
76 st_reading equ 3 ; Reading-*
77 st_awaiting equ 2 ; Reading-Wait
78 st_acking equ 1 ; Reading-Busy?, Stopping(from read)
79 st_stopping equ 0 ; Stopping
80 ; ...? means not always set in that state
86 ; computes slave address in form suitable for use in i2c controller
87 ; actual i2c slave address is (slave number) + 0b0001000
88 ; W slave number i2c address * 2
94 improper_read_done_data
97 ;======================================================================
106 mov_lw 0x08 ; !SSPEN, Master mode
108 clr_f SSPCON2 ; nothing going
109 mov_lw 0x80 ; SMP(noslew), !CKE(!smbus)
111 bc_f IPR1, SSPIP ; low priority
119 ; We have an interrupt:
121 i2cm_interrupt_definite
123 mov_ff SSPSTAT, sspstat
124 mov_ff SSPCON1, sspcon1
125 mov_ff SSPCON2, sspcon2
129 mov_lw (1<<WCOL) | (1<<SSPOV)
136 ; No ? Well, then the I2C should be idle now:
139 and_lw ~((1<<ACKSTAT) | (1<<ACKDT)) ; those two are ok if set
143 bt_f_if1 sspstat, R_W
146 bt_f_if1 st, st_stopping
147 bra m_event_done_stopping
149 bt_f_if1 st, st_starting
150 bra m_event_done_starting
153 bt_f_if1 st, st_addressing
154 bra m_event_done_addressing
156 bt_f_if1 st, st_acking
157 bra m_event_done_acking
159 bt_f_if1 st, st_writing
160 bra m_event_done_writing
162 bt_f_if1 st, st_reading
163 bra m_event_done_reading
168 ;========================================
169 ; MASTER - STARTING, ADDRESSING, STOPPING
173 ; st checked for busyness correct
174 ; st_reading/writing one set, one clear unchanged
175 ; st_starting clear set
177 ; slave any slave_number
178 ; expects to return directly to main program (caller)
183 bra_nz m_improper_slave
196 m_event_done_starting
200 bt_f_if1 st, st_reading
201 bs_w 0 ; address bottom bit means read
205 bs_f st, st_addressing
209 m_event_done_addressing
210 bt_f_if1 sspcon2, ACKSTAT
211 bra m_bad_address_ack
214 bc_f st, st_addressing
215 bt_f_if1 st, st_reading
216 bra m_event_done_addressing_read
217 bra m_event_done_addressing_write
221 ; st_stopping clear set
222 ; st_reading/acking/writing any unchanged
223 ; expects to return directly to main program or to end interrupt handler
229 m_event_done_stopping
237 ;========================================
243 ; State Idle/Reading-Wait Writing-Setup
246 bra m_write_start_busy
253 ; Did slave ack our byte ? It had better have done !
254 bt_f_if1 sspcon2, ACKSTAT
257 bs_f st, st_subsequent
260 m_event_done_addressing_write
262 ; st_addressing cleared
263 call i2cmu_write_next_byte
264 bra_z m_event_write_mustfinish
265 ; OK, we have the next byte:
271 m_event_write_mustfinish
272 bt_f_if0 st, st_subsequent
273 bra m_improper_write_finish
278 m_improper_write_finish
281 ;========================================
287 ; State Idle Reading-Busy
290 bra m_read_start_busy
299 bt_f_if1 st, st_awaiting
300 bra m_address_different
305 ; Main program would like to address another slave for reading.
307 tst_f_ifnz slave_next
312 m_event_done_addressing_read
313 m_event_done_acking_readmore
315 ; st_addressing/acking cleared
327 goto i2cmu_read_got_byte
331 ; State Reading-Wait Reading-Busy
332 bt_f_if0 st, st_awaiting
333 bra m_improper_read_another
334 ; OK, we're fine to read another:
338 ; st_reading 1 iff not done unchanged
339 ; st_awaiting still set cleared
340 ; st_acking clear set
341 ; expects to return directly to main program or to end interrupt handler
344 bc_f SSPCON2, ACKDT ; ACKDT=0 means to acknowledge
345 bt_f_if0 st, st_reading
346 bs_f SSPCON2, ACKDT ; don't ack last byte
352 ; State Reading-Wait Stopping
355 bt_f_if0 st, st_awaiting
356 bra improper_read_done_data
365 bt_f_if1 st, st_reading
366 bra m_event_done_acking_readmore
370 ; ok, we want to read another:
373 bt_f_if0 st, st_writing ; because of i2cm_write_start ?
374 bs_f st, st_reading ; no, then we will want to read
376 bra m_start_or_restart
379 m_improper_read_another
382 ;======================================================================
387 ; W slave number undefined
391 mov_lw 0x16 ; !SSPEN, CKP(release), I2C 7-bit slave no-SP-int
393 mov_lw 0x01 ; !GCEN, SEN
395 mov_lw 0x80 ; SMP(noslew), !CKE(!smbus)
397 bs_f IPR1, SSPIP ; high priority
399 ; Actually engages the I2C controller, which must already have
400 ; been set up (all but SSPEN):
401 ; SSPADD,SSPCON1,SSPCON2 configured correctly unchanged
402 ; SSPSTAT configured correctly unchanged, except:
403 ; SSPSTAT<SSPEN> 0 (disabled) 1 (enabled)
404 ; SSPIE 0 (disabled) 1 (enabled)
405 ; SSPIF configured correctly unchanged
406 ; TRISB<1,0> any configured for I2C
407 ; SSPIP any configured correctly
408 ; GIEL 0 (disabled) 0 (disabled)
409 ; ssp* shadows any all bits set
420 ;========================================
423 ; In general, we figure out our state and then see what kind of events
424 ; we were expecting. Bits we want to check:
425 ; 80 40 20 10 08 04 02 01
426 ; SMP CKE D_A P S R_W UA BF
427 ; set clr data? stop start read? clr full?
428 ; (we don't usually mention SMP, CKE and UA below)
430 ; Labels of the form s_event_* are branches of the interrupt
431 ; handler and are supposed to finish with return.
434 ; Macros: chkvals_start and chkval
436 chkvals_start macro chvals_what
440 chkval macro chkval_lastval, chkval_value, chkval_label
441 xor_lw chkval_value ^ chkval_lastval
448 s_write_slurpbyte macro
449 ; W any byte from master
450 ; i2c controller waiting due to SEN etc continuing with next byte
455 ;----------------------------------------
460 ;----------------------------------------
461 ; branches from the ISR
464 s_event_addrrecvwrite
466 goto i2csu_write_begin
469 s_event_reading_datanack
473 s_event_writing_datarecv
475 goto i2csu_write_data
479 i2cpanic morse_IH ; unknown high-priority interrupt
481 ;----------------------------------------
482 i2cs_interrupt ; 4cy interrupt latency + 3cy until branch to here
485 ; We have an interrupt:
487 mov_lw (1<<WCOL) | (1<<SSPOV)
491 ; Firstly, clear the interrupt flag so that if something else happens
492 ; while we faff, the interrupt will be regenerated:
495 chkvals_start SSPSTAT
496 chkval 0, 0x8c, i2csu_read_begin ;A,!P, S,R,!BF
497 chkval 0x8c,0xac, i2csu_read_another ;D,!P, S,R,!BF
498 chkval 0xac,0x89, s_event_addrrecvwrite ;A,!P, S,W,BF
499 chkval 0x89,0xa9, s_event_writing_datarecv ;D,!P, S,W,BF
500 chkval 0xa9,0xa8, s_event_reading_datanack ;D,!P, S,!R,!BF
504 ;======================================================================
506 include program+externs.fin
509 include variables+vars.fin