FDC37M607 datasheet(118/182 Pages) SMSC

118 / 182 page

118

GATEA20 AND KEYBOARD RESET

The FDC37M60x provides two options for

GateA20 and Keyboard Reset: 8042 Software

Generated GateA20 and KRESET and Port 92

Fast GateA20 and KRESET.

PORT 92 FAST GATEA20 AND KEYBOARD

RESET

Port 92 Register

This port can only be read or written if Port 92

has been enabled via bit 2 of the KRST_GA20

This register is used to support the alternate

reset (nALT_RST) and alternate A20 (ALT_A20)

functions.

Name

Port 92

Location

92h

Default Value

24h

Attribute

Read/Write

Size

8 bits

Port 92 Register

Bit

Function

7:6

Reserved. Returns 00 when read.

Reserved. Returns a 1 when read.

Reserved. Returns a 0 when read.

Reserved. Returns a 1 when read.

ALT_A20 Signal control. Writing a 0 to this bit causes the ALT_A20 signal to be

driven low. Writing a 1 to this bit causes the ALT_A20 signal to be driven high.

Alternate System Reset.

This read/write bit provides an alternate system reset

function. This function provides an alternate means to reset the system CPU to

effect a mode switch from Protected Virtual Address Mode to the Real Address

Mode. This provides a faster means of reset than is provided by the Keyboard

controller. This bit is set to a 0 by a system reset. Writing a 1 to this bit will cause

the nALT_RST signal to pulse acitive (low) for a minimum of 1 µs after a delay of

500 ns.

Before another nALT_RST pulse can be generated, this bit must be

written back to a 0.

nGATEA20

8042 P21

ALT_A20

System nA20M

FDC37M607 Datasheet(PDF) 118 Page - SMSC Corporation

FDC37M607 Datasheet(HTML) 118 Page - SMSC Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL