9
Electrical Description
Pin Function Description
RESET (RST, pin 1) Initializes the display.
FLASH (FL, pin 2) FL low indicates an access to the Flash RAM and is unaffected by the
state of address lines A
3
-A
4
.
ADDRESS INPUTS Each location in memory has a distinct address. Address inputs (A
0
-A
2
)
(A
0
-A
4
, pins 3-6, 10) select a specific location in the Character RAM, the Flash RAM or a
particular row in the UDC (User-Defined Character) RAM. A
3
-A
4
are used
to select which section of memory is accessed. Table 1 shows the
logic levels needed to access each section of memory.
Table 1. Logic Levels to Access Memory
Section of Memory FL A
4
A
3
A
2
A
1
A
0
Flash RAM 0 X X Char. Address
UDC Address Register 1 0 0 Don’t Care
UDC RAM 1 0 1 Row Address
Control Word Register 1 1 0 Don’t Care
Character RAM 1 1 1 Character Address
CLOCK SELECT Used to select either an internal (CLS = 1) or external (CLS = 0) clock source.
(CLS, pin 11)
CLOCK INPUT/OUTPUT Outputs the master clock (CLS = 1) or inputs a clock (CLS = 0) for slave displays.
(CLK, pin 12)
WRITE (WR, pin 13) Data is written into the display when the WR input is low and the CE input is low.
CHIP ENABLE (CE, pin 17) Must be at a logic low to read or write data to the display and must go high between
each read and write cycle.
READ (RD, pin 18) Data is read from the display when the RD input is low and the CE input is low.
DATA Bus (D
0
-D
7
, Used to read from or write to the display.
pins 19, 20, 23-28)
GND (SUPPLY) (pin 15) Analog ground for the LED drivers.
GND (LOGIC) (pin 16) Digital ground for internal logic.
V
DD
(POWER) (pin 14) Positive power supply input.
