Just complementing,
Hitachi Japan documentation, top of page 33 of the following PDF file
tells exactly:
Interfacing to a 4-bit MPU. The HD44780U can be connected to the I/O
port of a 4-bit MPU. [snip]... Note that two cycles are needed for the
busy flag check as well as for the data transfer.... [snip].
http://www.hitachi.co.jp/Sicd/English/Products/senyou/lcd/eHD44780U.pdf

--------------------------------------------------------
Wagner Lipnharski - UST Research Inc. - Orlando, Florida
Forum and microcontroller web site:  http://www.ustr.net
Microcontrollers Survey:  http://www.ustr.net/tellme.htm