Chapter 4 System Registers

The functions of the system registers are as follows:

● List of system registers

TV mode selection TVMR

Address: 100000H write-only (word)

Function: Specify the TV display mode

Update time: PTM at any time, VBE field

Framebuffer switching mode FBCR

Address: 100002H Write-only (word)

Function: Controls framebuffer switching and double-dense interlacing

Update time: FCM, FMT for each field, others frame buffer switching timing

Plot trigger PTMR

Address: 100004H Write-only (word)

Function: Controls the start of drawing

Update time: 01B write at any time, 00B, 10B write frame buffer switching timing

Erase Light Data EWDR

Address: 100006H Write-only (word)

Function: Specify the fill data of the frame buffer at the time of erase write

Update time: Frame buffer switching timing

Erase light upper left coordinates EWLR

Address: 100008H Write-only (word)

Function: Specify the upper left coordinate of the fill area of the frame buffer during erase write.

Update time: Frame buffer switching timing

Erase light lower right coordinates EWRR

Address: 10000AH write-only (word)

Function: Specify the lower right coordinates of the fill area of the frame buffer during erase write.

Update time: Frame buffer switching timing

Forced drawing end ENDR

Address: 10000CH write-only (word)

Function: Forced to end drawing

Update time: Anytime

Transfer end status EDSR

Address: 100010H Read-only (word)

Function: Currently, the fetch status of the end bit of the previous frame is displayed.

Update time:-

Processing interruption table address LOPR

Address: 100012H Read-only (word)

Function: Display the final processing command table address of the previous frame

Update time:-

Current processing table address COPR

Address: 100014H Read-only (word)

Function: Display the command table address currently being processed

Update time:-

Mode state MODR

Address: 100016H Read-only (word)

Function: Displays the set value in the write-only register

Update time:-

● Timing when the system register setting value is switched

The timing at which the system register settings take effect is as follows:

• Things that switch immediately
  Plot trigger mode (when writing PTM, 01B)
  TV mode selection (TVM)

  Things that switch every field (1/60 seconds)

  Framebuffer switching mode (FCM)

  Framebuffer switching trigger (FCT)

  Things that switch when switching frame buffers

  Plot trigger mode (when writing PTM, 00B or 10B)

  Even / odd coordinate selection bits (EOS)

  Dense interlacing enabled (DIE)

  Dense interlaced drawing line (DIL)

  Erase light data

  Erase light coordinates (upper left, lower right)

  V blank IN Switch after 1 line display after interrupt

  V Blank Erase Light Permit (VBE)