=> R0 = EOR mask
R1 = AND mask
<= R0 = old control value
R1 = new control value
This call controls power and miscallaneous features:
New value = (Old value AND R2) EOR R1
Value is a bitfield specifying:
bit meaning when set
0 Econet power enabled
1 LCD display power enabled
2 external video display power enabled
3 serial buffer and oscillator power enabled
4 dual panel mode
5,6 video clock control:
0 external clock
1 crystal ÷ 2
2 crystal
3 reserved
7 invert video clock
8 enable back light
9 display has 2 extra lines (else 1 extra)
10 2 DRAMs used for dual panel (else 1)
14 FDC oscillator power enabled
16 LCD palette set for inverse video
11-13,15,17-31 0 (reserved)
Changing bits 0, 3, 14 will generate Service_Portable.
The 82C711 shares one oscillator - this will only be powered down if bits 3 & 14 are both clear. On some machines the oscillator is used by other parts of the system and can never be powered down.
See PRM 4, page 200.
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