Control Registers Firmware Version Register The firmware version register is normally a read-only register containing the level of the firmware in the Z-80A. There is only one case where the host will write into this location. Before system initialization, the host should store a zero into this location (and the System Command register). When initialization is complete, the actual firmware version number will be stored in this location. This location may be tested to identify an uninitialized controller (or initialization in progress).
The version numbers will always be in the range of (1-63) .(0-7) where the version number occupies the five most significant bits, subversion the three least significant bits. Ivlvlvlvlvl Islslsl Controller Command Register The command register is an 8-bit register used to pass commands to all channels simultaneously. Handshaking is accomplished by setting bit 7 of the command. The host should insure that the last command has been executed (bit 7 = 0) before issuing a new command. Commands are:
o 1 2 3 4 5-127 disable controller enable controller disable interrupts enable interrupts reset interrupt unused Controller Status Register The status register is an 8-bit register used to pass status to the host concerning channel-independent information. The status bits are defined as follows: bit 0 bit 1 bit 2 Controller Enabled Interrupts enabled Interrupt pending (not qualified by bit 3 bits 4-7 "Interrupts enabled") Bus error not used - always 0 Interrupt Vector Register The Interrupt Vector Register is a l6-bit register containing data to allow quick response to an interrupting condition. The register is logically divided into three fields. 5-31