SD1200 Datasheet, PDF (28/35 Pages) List of Unclassifed Manufacturers – Analog-Interface XGA/SXGA TFT LCD Display Controller

SmartASIC, Inc.
SD1200
PRELIMINARY DATA SHEET
3.6. CPU interface
The SD1200 supports 2-wire I²C serial interface to external CPU. The interface
allows external CPU to access and modify control registers inside the SD1200. The
I²C serial interface is similar to the EEPROM interface, and the CPU is the host that
drives the SCL all the time as the clock and for “start” and “stop” bits. The SCL
frequency can be as high as 5MHz. The SDA is a bi-directional data wire. This
interface supports random and sequential write operations for CPU to modify one or
multiple control registers, and random and sequential read operations for CPU to read
all or part of the control registers.
The lower 4 bits of device ID for SD1200 are fixed at “1010”. The upper 3 bits are
programmable through MODE_IN3 (pin 19), MODE_IN2 (pin 18) and MODE_IN1
(pin 15). This avoids any conflict with other I2C devices on the same bus.
The following table briefly describes the SD1200 control registers. External CPU can
read these register to know the state of the SD1200 as well as the result of input mode
detection and phase calibration. External CPU can modify these control registers to
disable several SD1200 features and force the SD1200 into a particular state. When
the CPU modifies the control registers, the new data will be first stored in a set of
shadow registers, and then are copied into the actual control registers when the “CPU
Control Enable” bit is set. When the “CPU Control Enable” bit is set, the external
CPU will retain control and the SD1200 will not perform the auto mode detection and
auto calibration.
The external CPU is able to adjust the size of the output image and move the output
image up and down by simply changing the porch size and pixel and line numbers of
the input signal. These adjustments can be tied to the external user control button on
the monitor.
A set of four control registers are used to generate output signal when there is no input
signal available to the SD1200, or the input signal is beyond the acceptable ranges.
This operation mode is called standalone mode, which is very important for the end
users when they accidentally select an input mode beyond the acceptable range of the
SD1200, or when the input cable connection becomes loose for any reason. System
September, 1998
SmartASIC Confidential
28