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HCMS-2961 Datasheet(PDF) 8 Page - AVAGO TECHNOLOGIES LIMITED |
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HCMS-2961 Datasheet(HTML) 8 Page - AVAGO TECHNOLOGIES LIMITED |
8 / 16 page 8 Display Overview The HCMS-29xx series is a family of LED displays driven by on-board CMOS ICs. The LEDs are configured as 5 x 7 font characters and are driven in groups of 4 characters per IC. Each IC consists of a 160-bit shift register (the Dot Register), two 7-bit Control Words, and refresh circuitry. The Dot Register contents are mapped on a one-to-one basis to the display. Thus, an individual Dot Register bit uniquely controls a single LED. 8-character displays have two ICs that are cascaded. The Data Out line of the first IC is internally connected to the Data In line of the second IC forming a 320-bit Dot Register. The display’s other control and power lines are connected directly to both ICs. In 16-character displays, each row functions as an independent 8-character display with its own 320-bit Dot Register. Reset Reset initializes the Control Registers (sets all Control Register bits to logic low) and places the display in the sleep mode. The Reset pin should be connected to the system power-on reset circuit. The Dot Registers are not cleared upon power-on or by Reset. After power-on, the Dot Register contents are random; however, Reset will put the display in sleep mode, thereby blanking the LEDs. The Control Register and the Control Words are cleared to all zeros by Reset. To operate the display after being Reset, load the Dot Register with logic lows. Then load Control Word 0 with the desired brightness level and set the sleep mode bit to logic high. Dot Register The Dot Register holds the pattern to be displayed by the LEDs. Data is loaded into the Dot Register according to the procedure shown in Table 1 and the Write Cycle Timing Diagram. First RS is brought low, then CE is brought low. Next, each successive rising CLK edge will shift in the data at the DIN pin. Loading a logic high will turn the cor- responding LED on; a logic low turns the LED off. When all 160 bits have been loaded (or 320 bits in an 8-digit display), CE is brought to logic high. When CLK is next brought to logic low, new data is latched into the display dot drivers. Loading data into the Dot Register takes place while the previous data is displayed and eliminates the need to blank the display while loading data. Pixel Map In a 4-character display, the 160-bits are arranged as 20 columns by 8 rows. This array can be conceptualized as four 5 x 8 dot matrix character locations, but only 7 of the 8 rows have LEDs (see Figures 1 & 2). The bottom row (row 0) is not used. Thus, latch location 0 is never displayed. Column 0 controls the left-most column. Data from Dot Latch locations 0-7 determine whether or not pixels in Column 0 are turned-on or turned-off. Therefore, the lower left pixel is turned-on when a logic high is stored in Dot Latch location 1. Characters are loaded in serially, with the left-most character being loaded first and the right-most character being loaded last. By loading one character at a time and latching the data before loading the next character, the figures will appear to scroll from right to left. Table 1. Register Truth Table Function CLK CE RS Select Dot Register Not Rising L Load Dot Register DIN = HIGH LED = “ON” L X DIN = LOW LED = “OFF” Copy Data from Dot Register to Dot Latch L H X Select Control Register Not Rising H Load Control Register[1,3] L X Latch Data to Control Word[2] L X Notes: 1. BIT D0 of Control Word 1 must have been previously set to Low for serial mode or High for simultane- ous mode. 2. Selection of Control Word 1 or Control Word 0 is set by D7 of the Control Shift Register. The unselect- ed control word retains its previous value. 3. Control Word data is loaded Most Significant Bit (D7) first. ↑ ↓ ↑ ↓ ↑ ↓ ↑ ↓ ↑ ↓ |
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