AP1621

The AP1621 allows an easy connection of two C167 to the same external bus for sharing the same external memory resources, and the bus arbitration operation is enhanced to allow the C167CR to act as a slave. The master is defined as the one who is normally operating on the external bus, performing instruction fetches and data read/writes from/to the external memory. The slave is defined to normally execute out of internal resources, such as its internal ROM or RAM. Bus arbitration is required when the slave needs to also access portions of the external memory or XBUS peripherals of the master.

After reset, the master is normally starting execution out of external memory. During the initialization, the HLDEN bit in register PSW must be set. Since the HOLD# pin is held high through the external pullup, no hold requests can occur even when the slave is not initialized yet. If you want to know more information such as the electrical characteristics about the AP1621, please download the datasheet in www.seekic.com or www.chinaicmart.com .