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Both are 5V parts: Draws a maximum supply current of mA. When 0, data bus contains valid data. S5: Indicates condition of IF flag bits. S4-S3: Indicate which segment is accessed during current bus cycle:. INTA becomes active after current instruction completes.
Causes the interrupt vector to be put onto the data bus. NMI Non-maskable interrupt. Enables the most significant data bus bits D 15 -D 8 during a read or write operation. Commonly connected to the coprocessor. When 1, microprocessor stops and places address, data and control bus in high-impedance state. LOCK Lock output is used to lock peripherals off the system.
Activated by using the LOCK: prefix on any instruction. QS1 and QS0 The queue status bits show status of internal instruction queue. Provided for access by the numeric coprocessor RESET synchronization.
READY synchronization. Peripheral clock signal. Connection of the and the A second divide-by-2 counter 2. The ALE pin controls a set of latches. All signals MUST be buffered. Latches buffer for A 0 -A Data bus buffers must be bi-directional buffers BB. BHE : Selects the high-order memory bank. BUS Buffering and Latching. Dump data on data bus. Wait for memory access cycle.
During T 3 : This cycle is provided to allow memory to access data. If low, T 3 becomes a wait state. Otherwise, the data bus is sampled at the end of T 3. During T 4 : All bus signals are deactivated, in preparation for next bus cycle. Data is sampled for reads, writes occur for writes. The clock rate is 5MHz , therefore one Bus Cycle is ns. The transfer rate is 1. Memory specs memory access time must match constraints of system timing.
For example, bus timing for a read operation shows almost ns are needed to read data. However, memory must access faster due to setup times, e.
Address setup and data setup. This subtracts off about ns. Therefore, memory must access in at least ns minus another ns guard band for buffers and decoders. A wait state T W is an extra clock period inserted between T 2 and T 3 to lengthen the bus cycle. For example, this extends a ns bus cycle at 5MHz clock to ns. Maximum mode is designed to be used when a coprocessor exists in the system. Some of the control signals must be generated externally, due to redefinition of certain control pins on the The following pins are lost when the operates in Maximum mode.
MAX Mode System.
8288 - 8288 Bus Controller