AMD SC2200 Keyboard Support, 7.1 I/O Port 092h System Control, 7.2 I/O Port 061h System Control

Core Logic Module 32580B

6.2.7.1I/O Port 092h System Control

I/O Port 092h allows for a fast keyboard assertion of an A20# SMI and a fast keyboard CPU reset. Decoding for this register may be disabled via F0 Index 52h[3].

The assertion of a fast keyboard A20# SMI is controlled by either I/O Port 092h or by monitoring for the keyboard com- mand sequence (see Section 6.2.8.1 "Fast Keyboard Gate Address 20 and CPU Reset" on page 165). If bit 1 of I/O Port 092h is cleared, the Core Logic module internally asserts an A20M#, which in turn causes an SMI to the GX1 module. If bit 1 is set, A20M# is internally de- asserted, again causing an SMI.

The assertion of a fast keyboard reset (WM_RST SMI) is controlled by bit 0 in I/O Port 092h or by monitoring for the keyboard command sequence (write data = FEh to I/O port 64h). If bit 0 is changed from 0 to 1, the Core Logic module generates a reset to the GX1 module by generating a WM_RST SMI. When the WM_RST SMI occurs, the BIOS jumps to the Warm Reset vector. Note that Warm Reset is not a pin, it is under SMI control.

6.2.7.2I/O Port 061h System Control

Through I/O Port 061h, the speaker output can be enabled, the status of IOCHK# and SERR# can be read, and the state of the speaker data (Timer2 output) and refresh tog- gle (Timer1 output) can be read back. Note that NMI is under SMI control. Even though the hardware is present, the IOCHK# ball does not exist. Therefore, an NMI from IOCHK# can not happen.

6.2.7.3SMI Generation for NMI

Figure 6-10shows how the Core Logic module can gener- ate an SMI for an NMI. Note that NMI is not a pin.

6.2.8Keyboard Support

The Core Logic module can actively decode the keyboard controller I/O Ports 060h, 062h, 064h and 066h, and gener- ate an LPC bus cycle. Keyboard positive decoding can be disabled if F0 Index 5Ah[1] is cleared (i.e., subtractive decoding enabled).

6.2.8.1Fast Keyboard Gate Address 20 and CPU Reset

The Core Logic module monitors the keyboard I/O Ports 064h and 060h for the fast keyboard A20M# and CPU reset control sequences. If a write to I/O Port 060h[1] = 1 after a write takes place to I/O Port 064h with data of D1h, then the Core Logic module asserts the A20M# signal. A20M# remains asserted until cleared by any one of the following:

•A write to bit 1 of I/O Port 092h.

•A CPU reset of some kind.

•A write to I/O Port 060h[1] = 0 following a write to I/O Port 064h with data of D1h.

The fast keyboard A20M# and CPU reset can be disabled through F0 Index 52h[7]. By default, bit 7 is set, and the fast keyboard A20M# and CPU reset monitor logic is active. If bit 7 is clear, the Core Logic module forwards the commands to the keyboard controller.

By default, the Core Logic module forces the de-assertion of A20M# during a warm reset. This action may be dis- abled if F0 Index 52h[4] is cleared.

Parity Errors

F0 Index 04h[6]

AND

F0 Index 40h[1]

AND

PERR#

F0 Index 04h: PCI Command Register Bit 6 = PE (PERR# Enable)

Bit 8 = SE (SERR# Enable)

F0 Index 40h: PCI Function Control Register 1 Bit 1 = PES (PERR# Signals SERR#)

I/O Port 061h: Port B

Bit 2 = ERR_EN (PERR#/SERR# Enable) Bit 3 = IOCHK_EN (IOCHK Enable)

I/O Port 070h: RTC Index Register (WO) Bit 72 = NMI (NMI Enable)

					IOCHK#
	System Errors				(No External Connection)
				F0 Index 04h[8]			I/O Port 061h[3]
		AND				AND
			SERR#			NMI
OR

I/O Port 061h[2]

AND

NMI

OR

I/O Port 070h[7]

AND

SMI

Figure 6-10. SMI Generation for NMI

AMD Geode™ SC2200 Processor Data Book 165