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LMK04616: SYNC input functionality

Part Number: LMK04616

Hi,

I have a custom PCB using LMK04616 and I want to trigger SYSREF pulses on the rising edge of SYNC. I have the SYSREF registers set up correctly because I can trigger SYSREF pulses by setting the GLOBAL_SYSREF bit in GLBL_SYNC_SYSREF over SPI.

My problem is that when a rising edge appears at the SYNC pin, no SYSREF pulses are generated. As a debug step I have set STATUS0 to output a mirror of SYNC_INPUT, but the output remains low. I have also tried setting STATU0_INT_MUX to "Logic 1" and can confirm that the STATUS0 output then reads high.

I have also connected the SYNC input to a static 1V8 voltage, and STATUS0 remains low.

What am I doing wrong?

I have attached the registers exported from TICS.

Thanks very much,

Josh

lmk04616_regs.txt
R0	0x000000
R1	0x000100
R2	0x000200
R3	0x000306
R4	0x000438
R5	0x000503
R6	0x000615
R8	0x000800
R9	0x000900
R10	0x000A00
R12	0x000C51
R13	0x000D08
R16	0x00101F
R18	0x001206
R19	0x001300
R20	0x001482
R21	0x001508
R22	0x001650
R23	0x001719
R24	0x001802
R25	0x00190B
R26	0x001A0C
R27	0x001B00
R28	0x001CD0
R29	0x001D00
R30	0x001E64
R31	0x001F00
R32	0x002064
R33	0x002100
R34	0x002264
R35	0x002314
R36	0x002480
R37	0x002514
R38	0x002680
R39	0x002714
R40	0x002880
R41	0x002914
R42	0x002A80
R43	0x002B00
R44	0x002C10
R45	0x002D00
R46	0x002E1E
R47	0x002F01
R48	0x003001
R49	0x003100
R50	0x003200
R51	0x003310
R52	0x003443
R53	0x003510
R54	0x003643
R55	0x003710
R56	0x003843
R57	0x003900
R58	0x003A03
R59	0x003B18
R60	0x003C63
R61	0x003D14
R62	0x003E53
R63	0x003F00
R64	0x004003
R65	0x004100
R66	0x004203
R67	0x004302
R68	0x004400
R69	0x004500
R70	0x004604
R71	0x004702
R72	0x004800
R73	0x004900
R74	0x004A08
R75	0x004B00
R76	0x004C08
R77	0x004D00
R78	0x004E1E
R79	0x004F00
R80	0x005008
R81	0x005100
R82	0x005208
R83	0x005300
R84	0x005410
R85	0x005500
R86	0x00561A
R87	0x005700
R88	0x00583F
R89	0x005930
R90	0x005A1D
R91	0x005B32
R92	0x005C0E
R93	0x005D00
R94	0x005E01
R95	0x005F84
R96	0x006080
R97	0x006100
R98	0x006268
R99	0x006300
R100	0x006440
R101	0x006500
R102	0x006600
R103	0x006700
R104	0x006800
R105	0x006900
R106	0x006A00
R107	0x006B01
R108	0x006C00
R109	0x006D2C
R110	0x006E1B
R111	0x006F00
R112	0x007000
R113	0x007100
R114	0x00720A
R115	0x007300
R116	0x007420
R117	0x007500
R118	0x007601
R119	0x007701
R120	0x0078FF
R121	0x007900
R122	0x007A86
R123	0x007BA0
R124	0x007C08
R125	0x007D00
R126	0x007E00
R127	0x007F34
R128	0x008000
R129	0x008100
R130	0x008200
R131	0x008300
R132	0x00840F
R133	0x008501
R134	0x008601
R135	0x008700
R136	0x008840
R137	0x008900
R138	0x008A00
R139	0x008B40
R140	0x008C00
R141	0x008D00
R142	0x008E00
R143	0x008F40
R144	0x009000
R145	0x009100
R146	0x009280
R147	0x009382
R148	0x009404
R149	0x009509
R150	0x009610
R151	0x009720
R152	0x009820
R153	0x009980
R155	0x009B00
R156	0x009C20
R157	0x009D00
R158	0x009E00
R159	0x009F00
R160	0x00A000
R161	0x00A100
R162	0x00A200
R163	0x00A300
R164	0x00A400
R165	0x00A500
R166	0x00A600
R167	0x00A700
R168	0x00A800
R169	0x00A900
R170	0x00AA00
R171	0x00AB00
R172	0x00AC00
R173	0x00AD00
R174	0x00AE00
R175	0x00AF00
R176	0x00B001
R177	0x00B100
R178	0x00B200
R179	0x00B300
R180	0x00B402
R181	0x00B500
R182	0x00B600
R183	0x00B700
R184	0x00B800
R185	0x00B900
R186	0x00BA3F
R187	0x00BB0F
R188	0x00BC50
R189	0x00BD00
R190	0x00BE02
R191	0x00BF00
R192	0x00C000
R193	0x00C100
R194	0x00C200
R195	0x00C300
R196	0x00C400
R197	0x00C500
R198	0x00C600
R199	0x00C700
R200	0x00C800
R201	0x00C900
R202	0x00CA00
R203	0x00CB00
R204	0x00CC00
R205	0x00CD00
R206	0x00CE00
R207	0x00CF00
R208	0x00D000
R209	0x00D100
R210	0x00D200
R211	0x00D300
R212	0x00D400
R213	0x00D500
R214	0x00D600
R215	0x00D700
R216	0x00D800
R217	0x00D900
R218	0x00DA00
R219	0x00DB00
R220	0x00DC00
R221	0x00DD00
R222	0x00DE00
R223	0x00DF00
R224	0x00E000
R225	0x00E100
R226	0x00E200
R227	0x00E300
R228	0x00E400
R229	0x00E500
R230	0x00E600
R231	0x00E700
R232	0x00E800
R233	0x00E900
R234	0x00EA00
R235	0x00EB00
R236	0x00EC00
R237	0x00ED00
R238	0x00EE00
R239	0x00EF00
R240	0x00F000
R241	0x00F100
R242	0x00F200
R243	0x00F300
R244	0x00F400
R245	0x00F500
R246	0x00F600
R247	0x00F700
R248	0x00F800
R249	0x00F906
R250	0x00FAD7
R252	0x00FC00
R253	0x00FD00
R254	0x00FE00
R255	0x00FF00
R256	0x010000
R257	0x010100
R258	0x010200
R259	0x010300
R260	0x010400
R261	0x010500
R262	0x010600
R263	0x010700
R264	0x010800
R265	0x010900
R266	0x010A00
R267	0x010B00
R268	0x010C00
R269	0x010D00
R270	0x010E00
R271	0x010F00
R272	0x011000
R273	0x011100
R274	0x011200
R275	0x011300
R276	0x011400
R277	0x011500
R278	0x011600
R279	0x011700
R280	0x011800
R281	0x011900
R282	0x011A00
R283	0x011B00
R284	0x011C00
R285	0x011D00
R286	0x011E00
R287	0x011F00
R288	0x012000
R289	0x012100
R290	0x012200
R291	0x012300
R292	0x012401
R293	0x012500
R294	0x012600
R295	0x012705
R296	0x012805
R297	0x012905
R298	0x012A05
R299	0x012B05
R300	0x012C05
R301	0x012D05
R302	0x012E05
R303	0x012F00
R304	0x013000
R305	0x013100
R306	0x013200
R307	0x013300
R308	0x013400
R309	0x013500
R310	0x013600
R311	0x013700
R312	0x013800
R313	0x013900
R314	0x013A00
R315	0x013B00
R316	0x013C00
R317	0x013D00
R318	0x013E00
R319	0x013F00
R320	0x014005
R321	0x014112
R322	0x014260
R323	0x014300
R324	0x014400
R325	0x014500
R326	0x01463C
R327	0x014700
R328	0x014800
R329	0x014900
R330	0x014A00
R331	0x014B00
R332	0x014C00
R334	0x014E05
R335	0x014F00
R336	0x015000
R337	0x015100
R338	0x015200
R339	0x015300
R17	0x001101

  • Hi Josh,

    I see that you are writing 0x014260, which includes setting SYNC_ENB_INSTAGE=1. In the datasheet, the documentation claims that when this bit is set to 1, the SYNC input stage is disabled. Try setting 0x014240 instead.

    Regards,

    Derek Payne

  • Thanks Derek, that seems to have solved the issue!

    N.B. The reason I encountered this is because there seems to be a bug in TICS Pro (I am running v1.7.5.0). If I import my register set as uploaded above, then go to the "GPIO Pin: Sync" page, "SYNC_EN_INSTAGE" is correctly set to "Input 2-Level", despite the fact that SYNC_ENB_INSTAGE is set to 1 in register 0x142. if I regenerate the register output without changing anything SYNC_EN_INSTAGE remains set to 1.

    To get the correct register output I have to change "SYNC_EN_INSTAGE" to "Disabled", and then set it back to "Input 2-Level", only then do I get the correct values.