LM9830 datasheet(40/45 Pages) NSC

40 / 45 page

http://www.national.com

The correct Default Phase Difference (registers 52 and 53) must

be set for a scan to restart properly following a pause in the scan-

ning. See the LM9830 software for information on setting the

DPD register.

Attempting to read out the last pixels transferred into the SRAM

may cause the parallel port line buffer to underrun. Always make

sure there is at least 1K in buffer (register 01 >= 2) before reading

image data.

The number of fullsteps skipped at the start of a scan may be one

less than the Fullsteps to Skip at Start of Scan (registers 4A and

4B) setting.

The Scanning Step Size (registers 46 and 47) and Fast Feed

Step Size (registers 48 and 49) settings must be > 2.

When reverse is enabled, the LM9830 always stops on Red (line

rate color). When reverse is disabled, it will stop on any color.

The value in CR01 is reset by “start of scan reset” sos_reset.

sos_reset is asserted near the first line-end after a scan com-

mand is written (CR07=03). So if there is a residual value in

CR01, it will remain there for up to one line after a scan command

is written. CR07=08 (between scans) will reset CR01.

Some counters (register 01, notably), are not reset by the start of

a new scan until the first line has been scanned. For this reason

the chip should be briefly reset (register 07 = 08h) prior to a scan.

Make sure register 42 is set to the proper value (4 bit nibble or 8

bit bidirectional) for your PC’s parallel port mode before attempt-

ing to read data from the LM9830.

BUSY may go high by itself for the first few pixels after a scan is

started. After starting a scan, wait several ms before talking to the

LM9830.

When in 1 channel Mode A, the Dataport Target Color (reg03b1-

2) value is ignored for gamma reads and writes. The 1 Channel

Mode A Channel Color register (reg26b3-4) selects the gamma

table to be used when in 1 Channel Mode A. This only applies to

the gamma table. Register 3 is used to select the color for

gain/offset coefficient data.

Gamma and gain/offset coefficient data should be written with

coefficient data when scanning (register 7 = 3).

LM9830 Datasheet(PDF) 40 Page - National Semiconductor (TI)