ARM ARM DUI 0224I 4.6 Character LCD display

Programmer’s Reference

4.6 Character LCD display

This is a custom peripheral that provides an interface to a standard HD44780 16 x 2

character LCD module.

Note

The HD44780 display interface is very slow.

Requests to read or write data or a command to the character LCD are captured and

executed later. It is not until 500ns later that the access is completed. Poll access

complete flag (bit 0 of CHAR_RAW) or wait for a Char LCD interrupt on SIC7 to check

that the last access has completed.

After accepting a command, the character LCD typically requires 37μs to finish

processing. Some commands,

Return Home

for example, take substantially longer

(20ms). Poll the busy signal to determine when the display is ready for a new data or

command write.

An interrupt signal is generated by the character LCD controller a short time after the

raw data is valid. However this interrupt signal is reserved for future use and you must

use a polling routine instead of an interrupt service routine.

Table4-24 Character LCD display impl ementation

Property Value

Location FPGA

Memory base address

0x10008000

Interrupt NA

DMA NA

Release version custom logic

Reference documentation datasheet for the Hitachi HD44780 display (see also Character

LCD controller on page3-59)