| 摘要 |
PURPOSE:To increase a data transfer speed, by using local bursts consisting of NXM bytes for data transfer, and performing byte-by-byte data transfer when the remaining storage capacity of a data buffer memory decreases to >=(NXM- 1) bytes. CONSTITUTION:A host device 11 once knowing a data transfer request from a subordinate device checks the bit LAST of the condition register 1 of a subordinate device, and when it is ''0'', 4-byte when data to be transferred consists of >=4 bytes or data consisting of <=4 bytes when the data consists of <=4 bytes is sent to a 4-byte register 7. A control part 10 when detecting the remaining storage area of the data buffer memory decreases to <=3 from the counted value of a byte counter 9 sets a flip-flop 8 to change the bit LAST of the condition register 1 of the subordinate device into ''1''. The host device 11 once knows that the bit LAST has gone to 1'', switches every 4-byte data transfer to 1-byte data transfer. |
