1 ;######################################################################
2 ; i2clib.inc - I2C LIBRARY - DECLARATIONS AND DOCUMENTATION
5 ;============================================================
9 ; i2cm_... on master or i2cmu_... for upcalls
10 ; i2cs_... on slave or i2csu_... for upcalls
12 ; i2c?_... are for use by the rest of the program and
13 ; are the entrypoints which enable I2C use.
14 ; i2c?u_... must be defined in the rest of the program
15 ; with the functionality and behaviour described.
16 ; i2cm_... may only be called on the master PIC.
17 ; i2cs_... may only be called on slave PICs.
19 ; At all times following i2c[ms]_init, the i2c hardware in the PIC is
20 ; completely reserved to the routines defined in i2clib.asm. Nothing
21 ; else is allowed to read or modify the i2c controller state.
22 ; Likewise, the memory locations (variables) defined there are for use
23 ; by those routines only and must not be touched by the main program.
25 ; Unless otherwise stated, all routines accept any value in, and may
26 ; trash, W and the flags. All other registers and locations not
27 ; specifically mentioned here will be preserved by the
28 ; i2c?_... routines (and are therefore reserved for the rest of the
29 ; program). In all cases, routines are called with CALL or RCALL or
30 ; the equivalent, and routines are allowed to have subroutines (ie, to
31 ; use the call/return address stack).
33 ; Slave numbers (PIC numbers) are the actual PIC number, not the i2c
34 ; address. So, they start at 1 for the first slave. (PIC #0 is the
35 ; master but the master doesn't have an i2c address and its PIC number
36 ; is never required by or supplied to i2clib.)
37 ; They must be between 1 and 63 inclusive.
39 ; i2c?_... routines except i2c?_interrupt will never _directly_ call
40 ; any i2c?u_... routine; when we say `causes' this means that the
41 ; relevant i2c?u_... routine will be called at some later point from
42 ; i2c?_interrupt. i2c?u_... routines are allowed to call appropriate
43 ; i2c?_... routines (except i2c?_interrupt) directly if the context
46 ; All routines except i2c?_init must be called only:
47 ; * During an appropriate interrupt (high-priority for the slave;
48 ; low-priority for the master).
49 ; * From the main loop with those interrupts disabled; or
50 ; * From within an i2c?u_... routine (which are always called
51 ; from within i2c?_interrupt).
52 ; This is to avoid having one i2c_... routine running in an interrupt
53 ; which interrupted the middle of another i2c_... routine.
55 ; Some time between calling i2cs_init and waiting for the first event,
56 ; the main program should of course enable interrupts.
58 ;============================================================
59 ; COMMON ADMINISTRATIVE ROUTINES
64 ; Initialises the i2c system for use by a master PIC. Must be called
65 ; exactly once, which must be before any other i2c?_... function.
67 ; i2c controller any for use by i2clib
68 ; i2c interrupt config any enabled, low priority
69 ; global interrupt enable disabled unchanged
70 ; State Not-in-use Idle (as master)
75 ; Initialises the i2c system for use by a slave PIC. Must be called
76 ; exactly once, which must be before any other i2c?_... function.
77 ; W is the slave number.
79 ; i2c controller any for use by i2clib
80 ; i2c interrupt config any enabled, low priority
81 ; global interrupt enable disabled unchanged
82 ; State Not-in-use Idle (as slave)
87 extern i2cm_interrupt_definite
90 ; Must be called by the main program's interrupt handler;
91 ; high-priority for the slave or low-priority for the master.
93 ; For i2cm_interrupt, the main program's interrupt handler is
94 ; responsible for saving W and the flags register and other
95 ; interrupt-related administrivia. i2cm_interrupt checks for
96 ; SSPIF and handles any interrupt. i2cm_interrupt_definite
97 ; should only be called if SSPIF is set and handles it. In
98 ; both cases the ISR returns with `return'.
100 ; For i2cs_interrupt, it must be the only high-priority interrupt
101 ; source and expects to be called from the interrupt handler (and it
102 ; will return; the caller must retfie_r).
104 ; If there is an i2c interrupt, the i2c?_interrupt will service it, taking
105 ; any necessary action including calling appropriate
106 ; i2c?u_... routines, and clear the interrupt flag[*].
109 ; State any except Not-in-use may change
110 ; i2c interrupt state any cleared[*]
112 ; [*] The interrupt event on entry, if any, will be dealt with. If
113 ; interrupt processing takes a long time, another interrupt will occur
114 ; and this may result in the i2c interrupt flag being set on return
115 ; from i2c?_interrupt.
118 ;======================================================================
126 ; [Idle]<-------------------------<------.
128 ; / _ \ _____________________<______ |
130 ; write_start// \read_start | |
131 ; // \ ,------------------<---. | |
134 ; [Writing-Setup] [Reading-Busy]<---------. | | |
136 ; write_next_byte| |read_got_byte | | | |
137 ; must return NZ | | | | | |
139 ; ,-->[Writing] [Reading-Wait] | | | |
140 ; `-------' \ / || `.___________,' | | |
141 ; write_next_byte \ / || read_another | | |
142 ; returns NZ | / || | | |
143 ; | / |`.__________________,' | |
144 ; | | | read_start | |
145 ; write_next_byte| | `._____________________,' |
146 ; returns Z | | write_start |
151 ; `-------------------------------------'
153 ;--------------------
156 ; Called to notify that the previous conversation with the slave has
157 ; been finished as requested. The i2c system is now available and
158 ; i2cm_*_start can be called.
160 ; (Note: If this arrangment means that main program ends up needing to
161 ; keep track of whether the I2C is Idle or not, it would probably be
162 ; straightforward to enhance the interface to be enhanced to make that
163 ; unnecessary, since this information is already tracked by i2clib.)
166 ; State Stopping Idle
168 ;========================================
169 ; MASTER - WRITES (ie, transmission of data to the slave)
171 ;--------------------
172 extern i2cm_write_start
174 ; Requests that a slave be contacted for writing. When communication
175 ; has been established, i2cmu_write_next_byte will be called.
178 ; State Idle/Reading-Wait Writing-Setup
181 extern i2cmu_write_next_byte
183 ; Called to notify the main program that we are now ready to transmit
184 ; a byte to the slave that we're currently talking to. This may be
185 ; either because i2cm_write_start was previously called and
186 ; communication has been established, or because tranmission of the
187 ; previous byte is complete.
189 ; The main program must immediately supply the actual data byte. This
190 ; byte will then be transmitted to the slave, and then
191 ; i2cmu_write_next_byte will be called again.
193 ; Alternatively the main program may indicate that the tranmission
194 ; should finish by setting the Z flag on return. In this case the
195 ; slave will be told that this is the end of the message and the i2c
196 ; conversation will be finished. When the conversation is finished
197 ; and the bus and i2c controller are free again, i2cmu_done will be
200 ; When transmission should continue:
202 ; Beforehand At call On return After return
203 ; State Writing[-Setup] Writing Writing Writing
204 ; Status Z any 0 (NZ, not zero, not equal)
205 ; W any data for slave
207 ; When transmission should finish:
209 ; Beforehand At call On return After return
210 ; State Writing Writing Writing Stopping
211 ; Status Z any 1 (Z, zero, equal)
214 ;========================================
215 ; MASTER - READS (ie, reception of data from the slave)
217 ;--------------------
218 extern i2cm_read_start
220 ; Requests that a slave be contacted for reading. When communication
221 ; has been established and the first byte received,
222 ; i2cmu_read_got_byte will be called.
225 ; State Idle/Reading-Wait Reading-Busy
228 extern i2cmu_read_got_byte
230 ; Called to notify the main program that a byte has been recieved from
231 ; the slave PIC. The byte value is supplied. Communication with the
232 ; slave will be suspended (with the i2c bus blocked) until the main
233 ; program calls i2cm_read_another or i2cm_read_done. The main program
234 ; must call one of these two before doing anything else with the i2c.
237 ; State Reading Reading-Wait
240 extern i2cm_read_another
242 ; Requests that the communication with the slave continue and another
243 ; byte be read. When this is complete, i2cmu_read_got_byte will be
247 ; State Reading-Wait Reading-Busy
249 extern i2cm_read_done
251 ; Requests that reading from the slave be terminated. When the
252 ; conversation is finished and the bus and i2c controller are free
253 ; again, i2cmu_done will be called.
256 ; State Reading-Wait Stopping
259 ;======================================================================
271 ; |<----------------------------.
275 ; write_begin/ \read_begin |
278 ; ,->[Receiving] [Transmit-Wait]<-. |
280 ; write_data | |read_data | |
282 ; | [Transmit-Busy] | |
286 ; `----------+->---------------------'
288 ;========================================
289 ; SLAVE - WRITES (ie, reception of data from the master)
291 ;--------------------
292 extern i2csu_write_begin
294 ; Called to notify the main program that the master PIC has selected this
295 ; slave to talk to, for writing. There is no data at this stage; when
296 ; data is received, i2csu_write_data will be called.
298 ; Beforehand At call On return
299 ; State Idle Receiving Receiving
301 ;--------------------
302 extern i2csu_write_data
304 ; Called to notify the main program that the master PIC has
305 ; transmitted a byte of data. Provides the byte we received.
307 ; Beforehand At call On return
308 ; State Receiving Receiving Receiving
309 ; W data from master any
311 ;========================================
312 ; SLAVE - READS (ie, transmission of data to the master)
314 ;--------------------
315 extern i2csu_read_begin
317 ; Called to notify the main program that the master PIC has selected
318 ; this slave to talk to, for reading. The main program should invoke
319 ; i2cs_read_data with first byte of data that we should transmit to
323 ; State Idle Transmit-Wait
325 ;--------------------
326 extern i2cs_read_data
327 ; Transmits the byte of data to the master
329 ; Beforehand At call On return
330 ; State Transmit-Wait Transmit-Busy Transmit-Busy
331 ; W byte for master any
333 ; There is also a macro i2cs_read_data_macro
334 ; in i2clib.incm, which does the same thing.
336 ;--------------------
337 extern i2csu_read_another
339 ; Called to notify the main program that the master PIC has continued
340 ; by asking for another byte of data. The main program should once
341 ; more invoke i2cs_read_data.
344 ; State Transmit-Busy Transmit-Wait