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 a low-priority interrupt;
48 ; * From the main loop with low-priority interrupts disabled; or
49 ; * From within an i2c?u_... routine (which are always called
50 ; from within i2c?_interrupt).
51 ; This is to avoid having one i2c_... routine running in an interrupt
52 ; which interrupted the middle of another i2c_... routine.
54 ; Some time between calling i2cs_init and waiting for the first event,
55 ; the main program should of course enable interrupts.
57 ;============================================================
58 ; COMMON ADMINISTRATIVE ROUTINES
63 ; Initialises the i2c system for use by a master PIC. Must be called
64 ; exactly once, which must be before any other i2c?_... function.
66 ; i2c controller any for use by i2clib
67 ; i2c interrupt config any enabled, low priority
68 ; global interrupt enable disabled unchanged
69 ; State Not-in-use Idle
74 ; Initialises the i2c system for use by a slave PIC. Must be called
75 ; exactly once, which must be before any other i2c?_... function.
76 ; W is the slave number.
78 ; i2c controller any for use by i2clib
79 ; i2c interrupt config any enabled, low priority
80 ; global interrupt enable disabled unchanged
81 ; State Not-in-use Idle
87 ; Must be called by the main program's low priority interrupt handler.
88 ; The main program's interrupt handler is responsible for saving W and
89 ; the flags register and other interrupt-related administrivia. If
90 ; there is an i2c interrupt, this routine will service it, taking any
91 ; necessary action including calling appropriate i2c?u_... routines,
92 ; and clear the interrupt flag[*].
95 ; State any except Not-in-use may change
96 ; i2c interrupt state any cleared[*]
98 ; [*] The interrupt event on entry, if any, will be dealt with. If
99 ; interrupt processing takes a long time, another interrupt will occur
100 ; and this may result in the i2c interrupt flag being set on return
101 ; from i2c?_inerrupt.
104 ;======================================================================
113 ; [Idle]<-------------------------.
117 ; ,->[Receiving] [Transmitting]<-. |
118 ; `-----' | | `------' |
119 ; write_another | | read_another |
122 `--------------+->----------------'
124 ;========================================
125 ; SLAVE - WRITES (ie, reception of data from the master)
127 ;--------------------
128 extern i2csu_write_begin
130 ; Called to notify the main program that the master PIC has selected this
131 ; slave to talk to, for writing. Provides the first byte of data
132 ; we received from the master PIC.
134 ; Beforehand At call On return
135 ; State Idle Receiving Receiving
136 ; W data from master any
138 ;--------------------
139 extern i2csu_write_another
141 ; Called to notify the main program that the master PIC has continued
142 ; by transmitting another byte of data. Provides the byte we received.
144 ; Beforehand At call On return
145 ; State Receiving Receiving Receiving
146 ; W data from master any
148 ;--------------------
149 extern i2csu_write_done
151 ; Called to notify the main program that the master PIC has stopped
152 ; transmitting data (ie, finished the i2c conversation).
154 ; Beforehand At call On return
155 ; State Receiving Idle
157 ;========================================
158 ; SLAVE - READS (ie, transmission of data to the master)
160 ;--------------------
161 extern i2csu_read_begin
163 ; Called to notify the main program that the master PIC has selected
164 ; this slave to talk to, for reading, and to obtain the first byte of
165 ; data that we should transmit to the master.
167 ; Beforehand At call On return
168 ; State Idle Transmitting Transmitting
169 ; W any data for master
171 ;--------------------
172 extern i2csu_read_another
174 ; Called to notify the main program that the master PIC has continued
175 ; by asking for another byte of data. Must provide the byte.
177 ; Beforehand At call On return
178 ; State Transmitting Transmitting Transmitting
179 ; W any data for master
181 ;--------------------
182 extern i2csu_read_done
184 ; Called to notify the main program that the master PIC has stopped
185 ; asking for data (ie, finished receiving).
187 ; Beforehand At call On return
188 ; State Transmitting Idle
190 ;======================================================================
198 ; [Idle]<-----------------------------.
202 ; [Writing-Setup] [Reading-Busy]<---------. |
204 ; write_next_byte| |read_got_byte | |
205 ; must return NZ | | | |
207 ; ,-->[Writing] [Reading-Wait] | |
208 ; `-------' \ / `-------------' |
209 ; write_next_byte \ / read_another |
212 ; write_next_byte| | |
217 ; `----------------------------------'
219 ;--------------------
222 ; Called to notify that the previous conversation with the slave has
223 ; been finished as requested. The i2c system is now available and
224 ; i2cm_*_start can be called.
227 ; State Stopping Idle
229 ;========================================
230 ; MASTER - WRITES (ie, transmission of data to the slave)
232 ;--------------------
233 extern i2cm_write_start
235 ; Requests that a slave be contacted for writing. When communication
236 ; has been established, i2cmu_write_next_byte will be called.
239 ; State Idle Writing-Setup
242 extern i2cmu_write_next_byte
244 ; Called to notify the main program that we are now ready to transmit
245 ; a byte to the slave that we're currently talking to. This may be
246 ; either because i2cm_write_start was previously called and
247 ; communication has been established, or because tranmission of the
248 ; previous byte is complete.
250 ; The main program must immediately supply the actual data byte. This
251 ; byte will then be transmitted to the slave, and then
252 ; i2cmu_write_next_byte will be called again.
254 ; Alternatively the main program may indicate that the tranmission
255 ; should finish by setting the Z flag on return. In this case the
256 ; slave will be told that this is the end of the message and the i2c
257 ; conversation will be finished. When the conversation is finished
258 ; and the bus and i2c controller are free again, i2cmu_done will be
261 ; When transmission should continue:
263 ; Beforehand At call On return After return
264 ; State Writing[-Setup] Writing Writing Writing
265 ; Status Z any 0 (NZ, not zero, not equal)
266 ; W any data for slave
268 ; When transmission should finish:
270 ; Beforehand At call On return After return
271 ; State Writing Writing Writing Stopping
272 ; Status Z any 1 (Z, zero, equal)
275 ;========================================
276 ; MASTER - READS (ie, reception of data from the slave)
278 ;--------------------
279 extern i2cm_read_start
281 ; Requests that a slave be contacted for reading. When communication
282 ; has been established and the first byte received,
283 ; i2cmu_read_got_byte will be called.
286 ; State Idle Reading-Busy
289 extern i2cmu_read_got_byte
291 ; Called to notify the main program that a byte has been recieved from
292 ; the slave PIC. The byte value is supplied. Communication with the
293 ; slave will be suspended (with the i2c bus blocked) until the main
294 ; program calls i2cm_read_another or i2cm_read_done. The main program
295 ; must call one of these two before doing anything else with the i2c.
298 ; State Reading Reading-Wait
301 extern i2cm_read_another
303 ; Requests that the communication with the slave continue and another
304 ; byte be read. When this is complete, i2cmu_read_got_byte will be
308 ; State Reading-Wait Reading-Busy
310 extern i2cm_read_done
312 ; Requests that reading from the slave be terminated. When the
313 ; conversation is finished and the bus and i2c controller are free
314 ; again, i2cmu_done will be called.
317 ; State Reading-Wait Stopping
319 ;======================================================================