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Why does an error occurs in asynchronous mode when starting RxD pin?

Latest Updated:03/31/2009

Question:

When starting a RxD pin with low-hold, a framing error occurs in asynchronous mode for the serial interface. Why does this happen?

Answer:

For the serial interface in the H8 and H8S family, when a receive pin (a RxD pin) is low, start the receive operation to receive a break signal at the time the low pin was detected.

Next, a framing error occurs when the serial interface could not detect the STOP bit as “1” during STOP bit detection. 

Therefore, the serial interface can operate BREAK signal detection by checking if the received data is all 00s within framing error interrupt processing.

Also, be sure to clear the framing error flags to 0 when a high level is input to the RxD pin.

Please note that receive operation will be restarted to detect break signals when the error flag is cleared in low level.

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