1 extern QQ_detect_slave_init
2 extern QQ_i2csu_read_begin
3 extern QQ_i2csu_read_another
5 ;######################################################################
6 ; i2clib.inc - I2C LIBRARY - DECLARATIONS AND DOCUMENTATION
9 ;============================================================
13 ; i2cm_... on master or i2cmu_... for upcalls
14 ; i2cs_... on slave or i2csu_... for upcalls
16 ; i2c?_... are for use by the rest of the program and
17 ; are the entrypoints which enable I2C use.
18 ; i2c?u_... must be defined in the rest of the program
19 ; with the functionality and behaviour described.
20 ; i2cm_... may only be called on the master PIC.
21 ; i2cs_... may only be called on slave PICs.
23 ; At all times following i2c[ms]_init, the i2c hardware in the PIC is
24 ; completely reserved to the routines defined in i2clib.asm. Nothing
25 ; else is allowed to read or modify the i2c controller state.
26 ; Likewise, the memory locations (variables) defined there are for use
27 ; by those routines only and must not be touched by the main program.
29 ; Unless otherwise stated, all routines accept any value in, and may
30 ; trash, W and the flags. All other registers and locations not
31 ; specifically mentioned here will be preserved by the
32 ; i2c?_... routines (and are therefore reserved for the rest of the
33 ; program). In all cases, routines are called with CALL or RCALL or
34 ; the equivalent, and routines are allowed to have subroutines (ie, to
35 ; use the call/return address stack).
37 ; Slave numbers (PIC numbers) are the actual PIC number, not the i2c
38 ; address. So, they start at 1 for the first slave. (PIC #0 is the
39 ; master but the master doesn't have an i2c address and its PIC number
40 ; is never required by or supplied to i2clib.)
41 ; They must be between 1 and 63 inclusive.
43 ; i2c?_... routines except i2c?_interrupt will never _directly_ call
44 ; any i2c?u_... routine; when we say `causes' this means that the
45 ; relevant i2c?u_... routine will be called at some later point from
46 ; i2c?_interrupt. i2c?u_... routines are allowed to call appropriate
47 ; i2c?_... routines (except i2c?_interrupt) directly if the context
50 ; All routines except i2c?_init must be called only:
51 ; * During an appropriate interrupt (high-priority for the slave;
52 ; low-priority for the master).
53 ; * From the main loop with those interrupts disabled; or
54 ; * From within an i2c?u_... routine (which are always called
55 ; from within i2c?_interrupt).
56 ; This is to avoid having one i2c_... routine running in an interrupt
57 ; which interrupted the middle of another i2c_... routine.
59 ; Some time between calling i2cs_init and waiting for the first event,
60 ; the main program should of course enable interrupts.
62 ;============================================================
63 ; COMMON ADMINISTRATIVE ROUTINES
68 ; Initialises the i2c system for use by a master PIC. Must be called
69 ; exactly once, which must be before any other i2c?_... function.
71 ; i2c controller any for use by i2clib
72 ; i2c interrupt config any enabled, low priority
73 ; global interrupt enable disabled unchanged
74 ; State Not-in-use Idle (as master)
79 ; Initialises the i2c system for use by a slave PIC. Must be called
80 ; exactly once, which must be before any other i2c?_... function.
81 ; W is the slave number.
83 ; i2c controller any for use by i2clib
84 ; i2c interrupt config any enabled, low priority
85 ; global interrupt enable disabled unchanged
86 ; State Not-in-use Idle (as slave)
91 extern i2cm_interrupt_definite
94 ; Must be called by the main program's interrupt handler;
95 ; high-priority for the slave or low-priority for the master.
97 ; For i2cm_interrupt, the main program's interrupt handler is
98 ; responsible for saving W and the flags register and other
99 ; interrupt-related administrivia. i2cm_interrupt checks for
100 ; SSPIF and handles any interrupt. i2cm_interrupt_definite
101 ; should only be called if SSPIF is set and handles it. In
102 ; both cases the ISR returns with `return'.
104 ; For i2cs_interrupt, it must be the only high-priority interrupt
105 ; source and expects to be called from the interrupt handler (and it
106 ; will return; the caller must retfie_r).
108 ; If there is an i2c interrupt, the i2c?_interrupt will service it, taking
109 ; any necessary action including calling appropriate
110 ; i2c?u_... routines, and clear the interrupt flag[*].
113 ; State any except Not-in-use may change
114 ; i2c interrupt state any cleared[*]
116 ; [*] The interrupt event on entry, if any, will be dealt with. If
117 ; interrupt processing takes a long time, another interrupt will occur
118 ; and this may result in the i2c interrupt flag being set on return
119 ; from i2c?_interrupt.
122 ;======================================================================
130 ; [Idle]<-------------------------<------.
132 ; / _ \ _____________________<______ |
134 ; write_start// \read_start | |
135 ; // \ ,------------------<---. | |
138 ; [Writing-Setup] [Reading-Busy]<---------. | | |
140 ; write_next_byte| |read_got_byte | | | |
141 ; must return NZ | | | | | |
143 ; ,-->[Writing] [Reading-Wait] | | | |
144 ; `-------' \ / || `.___________,' | | |
145 ; write_next_byte \ / || read_another | | |
146 ; returns NZ | / || | | |
147 ; | / |`.__________________,' | |
148 ; | | | read_start | |
149 ; write_next_byte| | `._____________________,' |
150 ; returns Z | | write_start |
155 ; `-------------------------------------'
157 ;--------------------
160 ; Called to notify that the previous conversation with the slave has
161 ; been finished as requested. The i2c system is now available and
162 ; i2cm_*_start can be called.
164 ; (Note: If this arrangment means that main program ends up needing to
165 ; keep track of whether the I2C is Idle or not, it would probably be
166 ; straightforward to enhance the interface to be enhanced to make that
167 ; unnecessary, since this information is already tracked by i2clib.)
170 ; State Stopping Idle
172 ;========================================
173 ; MASTER - WRITES (ie, transmission of data to the slave)
175 ;--------------------
176 extern i2cm_write_start
178 ; Requests that a slave be contacted for writing. When communication
179 ; has been established, i2cmu_write_next_byte will be called.
182 ; State Idle/Reading-Wait Writing-Setup
185 extern i2cmu_write_next_byte
187 ; Called to notify the main program that we are now ready to transmit
188 ; a byte to the slave that we're currently talking to. This may be
189 ; either because i2cm_write_start was previously called and
190 ; communication has been established, or because tranmission of the
191 ; previous byte is complete.
193 ; The main program must immediately supply the actual data byte. This
194 ; byte will then be transmitted to the slave, and then
195 ; i2cmu_write_next_byte will be called again.
197 ; Alternatively the main program may indicate that the tranmission
198 ; should finish by setting the Z flag on return. In this case the
199 ; slave will be told that this is the end of the message and the i2c
200 ; conversation will be finished. When the conversation is finished
201 ; and the bus and i2c controller are free again, i2cmu_done will be
204 ; When transmission should continue:
206 ; Beforehand At call On return After return
207 ; State Writing[-Setup] Writing Writing Writing
208 ; Status Z any 0 (NZ, not zero, not equal)
209 ; W any data for slave
211 ; When transmission should finish:
213 ; Beforehand At call On return After return
214 ; State Writing Writing Writing Stopping
215 ; Status Z any 1 (Z, zero, equal)
218 ;========================================
219 ; MASTER - READS (ie, reception of data from the slave)
221 ;--------------------
222 extern i2cm_read_start
224 ; Requests that a slave be contacted for reading. When communication
225 ; has been established and the first byte received,
226 ; i2cmu_read_got_byte will be called.
229 ; State Idle/Reading-Wait Reading-Busy
232 extern i2cmu_read_got_byte
234 ; Called to notify the main program that a byte has been recieved from
235 ; the slave PIC. The byte value is supplied. Communication with the
236 ; slave will be suspended (with the i2c bus blocked) until the main
237 ; program calls i2cm_read_another or i2cm_read_done. The main program
238 ; must call one of these two before doing anything else with the i2c.
241 ; State Reading Reading-Wait
244 extern i2cm_read_another
246 ; Requests that the communication with the slave continue and another
247 ; byte be read. When this is complete, i2cmu_read_got_byte will be
251 ; State Reading-Wait Reading-Busy
253 extern i2cm_read_done
255 ; Requests that reading from the slave be terminated. When the
256 ; conversation is finished and the bus and i2c controller are free
257 ; again, i2cmu_done will be called.
260 ; State Reading-Wait Stopping
263 ;======================================================================
275 ; |<----------------------------.
279 ; write_begin/ \read_begin |
282 ; ,->[Receiving] [Transmit-Wait]<-. |
284 ; write_data | |read_data | |
286 ; | [Transmit-Busy] | |
290 ; `----------+->---------------------'
292 ;========================================
293 ; SLAVE - WRITES (ie, reception of data from the master)
295 ;--------------------
296 extern i2csu_write_begin
298 ; Called to notify the main program that the master PIC has selected this
299 ; slave to talk to, for writing. There is no data at this stage; when
300 ; data is received, i2csu_write_data will be called.
302 ; Beforehand At call On return
303 ; State Idle Receiving Receiving
305 ;--------------------
306 extern i2csu_write_data
308 ; Called to notify the main program that the master PIC has
309 ; transmitted a byte of data. Provides the byte we received.
311 ; Beforehand At call On return
312 ; State Receiving Receiving Receiving
313 ; W data from master any
315 ;========================================
316 ; SLAVE - READS (ie, transmission of data to the master)
318 ;--------------------
319 extern i2csu_read_begin
321 ; Called to notify the main program that the master PIC has selected
322 ; this slave to talk to, for reading. The main program should invoke
323 ; i2cs_read_data with first byte of data that we should transmit to
327 ; State Idle Transmit-Wait
329 ;--------------------
330 extern i2cs_read_data
331 ; Transmits the byte of data to the master
333 ; Beforehand At call On return
334 ; State Transmit-Wait Transmit-Busy Transmit-Busy
335 ; W byte for master any
337 ; There is also a macro i2cs_read_data_macro
338 ; in i2clib.incm, which does the same thing.
340 ;--------------------
341 extern i2csu_read_another
343 ; Called to notify the main program that the master PIC has continued
344 ; by asking for another byte of data. The main program should once
345 ; more invoke i2cs_read_data.
348 ; State Transmit-Busy Transmit-Wait