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Does the RES# pin need to set to low level to enter hardware standby mode?

Latest Updated:03/06/2008

Question:

Does the RES# pin need to be set to low level in order to enter hardware standby mode?

Answer:

No, the RES# pin does not need to be set to low level beforehand. However, if the STBY# pin is set to low, the MCU will switch to hardware standby mode and the internal clock to asynchronous, regardless of MCU operating state. Consequently, if, for example, the STBY# pin were set to low while the CPU was in the process of accessing on-chip RAM, that data could be lost. There are two methods for preserving on-chip RAM contents, detailed as follows: 1) Switch to standby mode after stopping the CPU from accessing on-chip RAM by setting the RAME bit to 0 before setting the STBY# pin to low; and 2) Set the RES# pin to low before setting the STBY# pin to low . In addition, as long as the prescribed voltage (RAM standby voltage) is received in hardware standby mode, RAM contents will be preserved.
Suitable Products
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/2615
H8S/2612
H8S/2556, 2552, 2506
H8S/2378, 2378R
H8S/2368
H8S/2398, 2357
H8S/2355
H8S/2350
H8S/2345
H8S/2339
H8S/2329
H8S/2319
H8S/2282, 2280
H8S/2268, 2264
H8S/2258, 2239, 2238, 2237, 2227
H8S/2245
H8S/2215
H8S/2214
H8S/2218, 2212
H8S/2189R
H8S/2172
H8S/2168
H8S/2148, 2144
H8S/2144B,2134B
H8S/2140B
H8S/2138, 2134
H8S/2125
H8S/2128, 2124
H8S/2117, 2117R
H8S/2116
H8S/2114R
H8S/2111B
H8S/2110B
H8SX/1663
H8SX/1657
H8SX/1653
H8SX/1650, H8SX/1651
H8SX/1648A, H8SX/1648L
H8SX/1638, H8SX/1638L
H8SX/1544