HCMS-2975_13 Datasheet, PDF (9/16 Pages) AVAGO TECHNOLOGIES LIMITED – High Performance CMOS 5 x 7 Alphanumeric Displays

HCMS-29xx Write Cycle Diagram
RS
CE
CLK
D _IN
D OUT (SERIAL)
D _OUT
(SIMULTANEOUS)
T_RSS T_RSH
1
2
T_CLKCE
3
T_CES
4
TCLKH
11
T_CEDO
10
T_DS
T_DH
6
7
T_DOUT
8
T_DOUTP
9
T_CLKL
12
T_CEH
5
[1]
NEW DATA LATCHED HERE
LED OUTPUTS,
CONTROL
REGISTERS
PREVIOUS DATA
NOTE:
1. DATA IS COPIED TO THE CONTROL REGISTER OR THE DOT LATCH AND LED OUTPUTS WHEN CE IS HIGH AND CLK IS LOW.
NEW DATA
Control Register
The Control Register allows software modification of the
IC’s opera­tion and consists of two independent 7‑bit
control words. Bit D₇ in the shift register selects one of
the two 7‑bit control words. Control Word 0 performs
pulse width modula­tion brightness control, peak pixel
current brightness control, and sleep mode. Control Word
1 sets serial/simultaneous data out mode, and external
oscilla­tor prescaler. Each function is independent of
the others.
Control Register Data Loading
Data is loaded into the Control Register, MSB first, ac-
cording to the proce­dure shown in Table 1 and the
Write Cycle Timing Diagram. First, RS is brought to logic
high and then CE is brought to logic low. Next, each
successive rising CLK edge will shift in the data on the
D_IN pin. Finally, when 8 bits have been loaded, the CE
line is brought to logic high. When CLK goes to logic
low, new data is copied into the selected control word.
Loading data into the Control Register takes place while
the previous control word configures the display.
Control Word 0
Loading the Control Register with D₇ = Logic low se-
lects Control Word 0 (see Table 2). Bits D₀‑D₃ adjust the
display brightness by pulse width modulating the LED
on-time, while Bits D₄‑D₅ adjust the display brightness
by changing the peak pixel current. Bit D₆ selects normal
operation or sleep mode.
Sleep mode (Control Word 0, bit D₆ = Low) turns off the
Internal Display Oscillator and the LED pixel drivers. This
mode is used when the IC needs to be powered up, but
does not need to be active. Current draw in sleep mode
is nearly zero. Data in the Dot Register and Control Words
are retained during sleep mode.