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★ HARDWARE Manual ★ VDP1 User's Manual
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VDP1 User's Manual/Chapter 4 System Registers

■4.9 Mode status register

The mode status register (MODR) represents the setting value of a write-only register. It is a read-only 16-bit register located at address 100016H.

 MODR
 100016H
 (R)
 bit15
 bit14
 bit13
 bit12
 bit11
 bit10
 bit9
 bit8
 bit7
 bit6
 bit5
 bit4
 bit3
 bit2
 bit1
 bit0
VER - - - PTM1 EOS DIS DIL FCM VBE TVM

The registers at addresses 100000H to 10000CH are write-only, so you cannot read them to check the set values. The setting value of the write-only register can be checked with this register. It can mainly be used as help information during program development. However, this value is the system register setting value itself, and may differ from the value imported as an internal signal depending on the timing of frame switching, etc.

Version number: version number(VER), bits 15-12

Indicates the version number of VDP1. The value is 1 (0001B).

Plot trigger mode upper: PTM1, bit 8

This is the setting value of bit 1 of PTMR (plot trigger register: 100004H).

Even/odd coordinate selection bit: EOS, bit 7

This is the setting value of bit 4 of FBCR (frame buffer switching mode register: 100002H).

Double-dense interlace enable bit: DIE, bit 6

This is the setting value of bit 3 of FBCR (frame buffer switching mode register: 100002H).

Double-dense interlaced drawing line: DIL, bit 5

This is the setting value of bit 2 of FBCR (frame buffer switching mode register: 100002H).

Frame buffer switching mode bit: FCM, bit 4

This is the setting value of bit 1 of FBCR (frame buffer switching mode register: 100002H).

V blank erase write enable bit: VBE, bit 3

This is the setting value of bit 3 of TVHR (TV mode selection register: 100000H).

TV mode selection bits: TVM, bits 2-0

This is the setting value of bits 2 to 0 of TVHR (TV mode selection register: 100000H).

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