The purpose of this lab is to become familiar with the 2×16 character display and to integrate and adapt code from the previous 2 labs. You may work in pairs and submit a group report.
In this lab, you will design, code, assemble, link, download, and run a program. The program you will be writing is a display animation program. Specifically, you will scroll a message of more than 16 characters across the first line of the 2×16 character display.
Begin by carefully studying the sample program. Download it into your “ROOT”\lab3 directory and try it on your Fox11. You will also need to download wytec.s and place it in your “ROOT” directory. Note that the LCD_LINE1 routine “clobbers” registers D (A:B) and X. This can be a problem if you have important values in those registers. A solution is to save copies of the important values before calling the subroutine and to restore them after. This can be done using the stack.
psha ; Save important value from A to stack
pshx ; Same for X
jsr LCD_LINE1 ; LCD_LINE1 destroys D (A:B) and X. Y is untouched.
pulx ; Restore important value from stack to X (stack/nested order)
pula ; Same for A
Use the time delay (wait) routine from the last lab so that there is enough time to see that your message is scrolling. You are only required to scroll the message once, but may scroll it repeatedly or cause it to bounce back and forth if you wish. You may adapt the strnlen code from the first lab to calculate the length of the string, which will allow you to calculate the number of frames to display. Or, you may just check for the NUL character at the end of your .asciz string.
For example, if your string is “Quis custodiet ipsos custodes?”, your successive frames would be…
Quis custodiet i uis custodiet ip is custodiet ips s custodiet ipso custodiet ipsos custodiet ipsos ustodiet ipsos c stodiet ipsos cu todiet ipsos cus odiet ipsos cust diet ipsos custo iet ipsos custod et ipsos custode t ipsos custodes ipsos custodes?
The display on the Fox11 uses the ubiquitous Hitachi chipset. Specifically, the display is manufactured by Hantronix. As can be seen in the sample program for this lab, we are interfacing with the display at a fairly high level using routines in the Fox11 ROM. LCD_SPEC.PDF on your Fox11 CD (or in your Ep2IDE/document folder after installation) contains a wealth of information about the display, but, for the current lab, page 8 in the PDF is of interest. It shows that the Hitachi chipset supports all of the standard ASCII characters, plus a number of Japanese and scientific characters. For comparison, here is the 7-bit ASCII character set.
