Return to previous page ｜ Return to menu ｜ Go to next page

■ 4.9 Mode status register

Mode status register (MODR, Mode register) indicates the setting value of the write-only register. This is a read-only 16-bit register at address 100016H.

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

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
Setting value of bit 1 of PTMR (Plot trigger register: 100004H).

Even / odd coordinate selection bit: EOS, bit 7
Setting value of bit 4 of FBCR (frame buffer switching mode register: 10002H).

Double dense interlace enable bit: DIE, bit 6
Setting value of bit 3 of FBCR (frame buffer switching mode register: 10002H).

Double dense interlace drawing line: DIL, bit 5
Setting value of bit 2 of FBCR (frame buffer switching mode register: 10002H).

Frame buffer switching mode bit: FCM, bit 4
Setting value of bit 1 of FBCR (frame buffer switching mode register: 10002H).

Return to previous page ｜ Return to menu ｜ Go to next page