Open the command line window by going to the HEW menu bar and selecting [Display] -> [Command Line].
By using the command described below you can write to the I/O register without initiating a read.
(However, when using E8/E8a emulators, this is only effective for the H8 Family.)
Command: hdi memwrite
This command writes data to the target system memory.
hdi memwrite space address size data
Functions for the hdi memwrite command is as follows:
Space: specify the address of the space to be used. This is only for processors that have multiple address spaces. For single address space processors, specify "0".
Address: address of first data to be written.
Size: size of data to be written; 1 = byte, 2 = word, 4 = long word
Data: data to be written; A successful write will return an empty character string. An error will return an error character string.
hdi memwrite 0 ff00 1 ff
(when writing byte-data H'FF to address H'FF00)
If the target address is displayed in the memory window or I/O register window at this point, a read event has occurred.