Epson LQ-2550 Technical Manual page 103

2.3.3.1 LED Drive Section
Each LED is controlled and driven
register and LED drivers.
Figure 2-52 shows the data transfer timing for the MSM59371, and Figure 2-53 shows a block diagram
of the MSM5937 1.
The MSM59371 converts 16-bit serial data (DATA IN) from the sub CPU into parallel data using a
synchronous clock (CLK) and trigger signal (LOAD), then outputs the data to the output ports (O 1 to O 16).
Output ports 01 to 014 are used to drive the LEDs, and 015 and 016 are for the signals that control
the reading of the switch states.
015
016
DATA IN
*1 LED7 LED19 LEO 11 LEO lO LE09 LE016 LE?!15 LE~l 4 LEW13 L::6 L8~5 L~~4 L~~3 L~~8
* '
LOAD
NOTES: 1. An LED turns on when the data bit is "1".
2. Refer to Table A-41 for the layout of the LEDs.
DATA IN
D1
RESET
LOAD
01
by port expander driver IC MSM59371, which includes a 16-bit shift
014 013 012 011 09
I n d i c a t e s a n o l d v a l u e .
Figure 2-52. MSM59371 Data Transfer Timing
D2 D3 D5
16-BIT LATCHES WITH RESET
I
02 03 04 05
Figure 2-53. MSM59371 Block Diagram
D6 D7 Da D9
I I
06 07 08 09 010
2-56
a n e w v a l u e .
I
D1 1
I I
011 012 013 014 015"
1
016