HD66724 Datasheet, PDF (19/117 Pages) Hitachi Semiconductor – (Graphics LCD Controller/Driver with Key Scan Function)

HD66724/HD66725
Block Function Description
System Interface
The HD66724/HD66725 have five types of system interfaces, and a clock-synchronized serial, a 68-system
4-bit/8-bit bus, and a 80-system 4-bit/8-bit bus. The interface mode is selected by the IM2-0 pins. The key
scan of the HD66724/HD66725 are not available for the 4-bit/8-bit bus interface. Instead, use the clock-
synchronized serial interface.
The HD66724/HD66725 have two 8-bit registers: an instruction register (IR) and a data register (DR).
The IR stores instruction codes, such as clear display, display control, and address information for the
display data RAM (DDRAM), character generator RAM (CGRAM), and segment RAM (SEGRAM).
The DR temporarily stores the data to be written to and read from the DDRAM, CGRAM, or SEGRAM.
The data written to the DR from the MPU is automatically written to the DDRAM, CGRAM, or SEGRAM
by internal operation. Since the data is read from the RAM through the DR, the first read data is invalid and
the second read data is valid. After reading, the data in DDRAM, CGRAM, or SEGRAM at the next
address is sent to the DR for the next reading from the MPU.
Execution time for instruction excluding clear display is 0 clock cycle and instructions can be written in
succession.
Table 3 Register Selection by RS and R/W Bits
R/W Bits
0
1
0
1
RS Bits
0
0
1
1
Operations
Writes an instruction to the IR
Reads key scan data (SCAN0-3)
Writes the data to the DR to DDRAM, CGRAM, or SEGRAM
Reads the data from the DDRAM, CGRAM, or SEGRAM to DR
Key Scan Registers (SCAN0 to SCAN3)
The key matrix scanner senses and holds the key states at each rising edge of key strobe signals KST0 to
KST3 that are output by the HD66724/HD66725. After passing through the key matrix, these strobe signals
are used to sample the key states on eight inputs from KIN0 to KIN7, enabling up to 32 keys to be scanned.
Key states KIN0 to KIN7 are sampled by key strobe signal KST0 and latched into register SCAN0.
Similarly, the data sampled by strobe signals KST1 to KST3 is latched into registers SCAN1 to SCAN3,
respectively. For details, see the Key Scan Control section.
General Output Ports (PORT0 to PORT 2)
The HD66724/HD66725 have three general output ports. These ports control drive current such as that for
LEDs or backlighting by using the current boosted by an external transistor.
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