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How to output 8 clocks to receive data continuously?

Latest Updated:03/31/2009

Question:

I would like to use the serial interface of the H8 family and H8S family for synchronous receive, but a few extra clocks are output from the SCK pin (serial clock). Is there a good idea about how to output 8 clocks every single time?

Answer:

When the serial interface of the H8 family and the H8S family fulfills three conditions, which is in synchronous, set to SCK output, and in receive mode (TE=0, RE=1), the SCK output will be in a continuous output state in order to be able to receive continuously. So, if the serial interface misses the timing to stop the SCK output, it would look like extra synchronous output.

The best solution for this problem would be to set the serial interface to transmit/receive mode (TE=1, RE=1) first, and dummy write the transmit data (H’FF).

There will be no effect on the transmit line since the transmit data is H’FF.

In transmit/receive mode, transmitting is prioritized so the clock is outputted as transmit data is arranged.

Therefore every single time, just only 8 clocks will be outputted perfectly.

There are two more other ways to solve. The second solution is forcing the serial interface to stop by producing an overrun error intentionally. In this case, the SCK clock output will be stopped after 16 clocks without fail.

However, valid/invalid data should be prepared in advance at the transmitter.

The third solution is to lower the communication speed of synchronous so that the program can catch the timing. However, as we mentioned before, the first solution would be the best way because it does not need to depend on communication speed.

Suitable Products
H8 Family
H8/300H
H8/3069R
H8/3068
H8/3067(H8/3065, H8/3066, H8/3067)
H8/3062(H8/3060, H8/3061, H8/3062)
H8/3052B
H8/3048B
H8/3048(H8/3044, H8/3045, H8/3047, H8/3048)
H8/3042(H8/3040, H8/3041, H8/3042)
H8/3039(H8/3036, H8/3037, H8/3038, H8/3039)
H8/3035(H8/3033, H8/3034, H8/3035)
H8/3032(H8/3030, H8/3031, H8/3032)
H8/3029F
H8/3029
H8/3028(H8/3028, H8/3028F)
H8/3024(H8/3024, H8/3026)
H8/3022(H8/3020, H8/3021, H8/3022)
H8/3008
H8/3006(H8/3006, H8/3007)
H8/3004(H8/3004, H8/3005)
H8/3003
H8/3002
H8/3001
H8S Family
H8S/2600
H8S/2678, 2678R
H8S/2668
H8S/2655
H8S/2649
H8S/2648, 2646
H8S/2643
H8S/2630, 2639, 2638, 2636, 2635
H8S/2633
H8S/2628
H8S/2626, 2623
H8S/2615
H8S/2612
H8S/2500
H8S/2556, 2552, 2506
H8S/2400
H8S/2437
H8S/2300
H8S/2378, 2378R
H8S/2368
H8S/2398, 2357
H8S/2355
H8S/2350
H8S/2345
H8S/2339
H8S/2329
H8S/2319
H8S/2200
H8S/2282, 2280
H8S/2276
H8S/2268, 2264
H8S/2258, 2239, 2238, 2237, 2227
H8S/2245
H8S/2215
H8S/2214
H8S/2218, 2212
H8S/2100
H8S/2199R
H8S/2194
H8S/2189R
H8S/2172
H8S/2168
H8S/2169, 2149
H8S/2158
H8S/2148, 2144
H8S/2144B,2134B
H8S/2140B
H8S/2138, 2134
H8S/2128, 2124
H8S/2114R
H8S/2111B
H8S/2110B