ACCESSING METHOD TO 8-BIT AND 16-BIT PERIPHERAL DEVICES BY 16-BIT MICROPROCESSOR

摘要

PURPOSE:To use a memory or an I/O in a 8-bit group as it is regarding an 8-bit peripheral device as a peripheral device provided with the data width of 16 bits when the 8-bit peripheral device is observed from a 16-bit MPU. CONSTITUTION:An address control part 11 sends 2n obtained by doubling address information (n) to an address information line 21. An R/W control part 5 reads out information in address 2n of an 8-bit peripheral device 13 on an 8-bit data bus 22 and controls a command line 16 to latch the read-out information in an 8-bit latch 8. The command control part 5 sends an R signl to a command line 19, reads out information in address (2n+1) of the 8-bit peripheral device 13 on the 8-bit data bus 22, turns a two-way buffer 9 from the 8-bit peripheral device 13 to the MPU4 through a command line 17, and transmits the information on the bus 22 to a bus 2. Then, the control part 5 releases the waiting state of the MPU4 to input the data of the latch 8 and the information on the bus 22 to the MPU4.