AMD SC1200 Configuration Structure / Access, Index-Data Register Pair, SIO Configuration Options

32579B SuperI/O Module

5.3Configuration Structure / Access

This section describes the structure of the configuration register file, and the method of accessing the configuration registers.

5.3.1Index-Data Register Pair

The SIO configuration access is performed via an Index- Data register pair, using only two system I/O byte locations. The base address of this register pair is determined according to the state of the IO_SIOCFG_IN bit field of the Core Logic module (F5BAR0+I/O Offset 00h[26:25]). Table 5-1shows the selected base addresses as a function of the IO_SIOCFG_IN bit field.

Table 5-1. SIO Configuration Options

	I/O Address
IO_SIOCFG_IN	Index	Data
Settings	Register	Register	Description
00	-	-	SIO disabled
01	-	-	Configuration
			access disabled
10	002Eh	002Fh	Base address 1
			selected
11	015Ch	015Dh	Base address 2
			selected

The Index Register is an 8-bit R/W register located at the selected base address (Base+0). It is used as a pointer to the configuration register file, and holds the index of the configuration register that is currently accessible via the

Table 5-2. LDN Assignments

LDN	Functional Block	Reference
00h	Real-Time Clock (RTC)	Page 98
01h	System Wakeup Control (SWC)	Page 100
02h	Infrared Communication Port	Page 101
	(IRCP) or Serial Port 3 (SP3)
03h	Serial Port 1 (SP1)	Page 102
05h	ACCESS.bus 1 (ACB1)	Page 103
06h	ACCESS.bus 2 (ACB2)
07h	Parallel Port (PP)	Page 104
08h	Serial Port 2 (SP2)	Page 102

Figure 5-3shows the structure of the standard PnP config- uration register file. The SIO Control And Configuration registers are not banked and are accessed by the Index- Data register pair only (as described above). However, the Logical Device Control and Configuration registers are duplicated over eight banks for eight logical devices. There- fore, accessing a specific register in a specific bank is per- formed by two-dimensional indexing, where the LDN register selects the bank (or logical device), and the Index register selects the register within the bank. Accessing the Data register while the Index register holds a value of 30h or higher results in a physical access to the Logical Device Configuration registers currently pointed to by the Index register, within the logical device bank currently selected by the LDN register.

Data Register. Reading the Index Register returns the last value written to it (or the default of 00h after reset).

The Data Register is an 8-bit virtual register, used as a data path to any configuration register. Accessing the data register results with physically accessing the configuration register that is currently pointed by the Index Register.

5.3.2Banked Logical Device Registers

Each functional block is associated with a Logical Device Number (LDN). The configuration registers are grouped into banks, where each bank holds the standard configura- tion registers of the corresponding logical device. Table 5-2shows the LDNs of the device functional blocks.

07h

20h

2Fh

30h

60h

63h

70h

71h

74h

75h

F0h

FEh

Logical Device Number Register

SIO Configuration Registers

Logical Device Control Register

Standard Logical Device

Standard Registers

Special (Vendor-defined)

Logical Device

Configuration Registers

Bank

Select

Banks

(One per Logical Device)

Figure 5-3. Standard Configuration Register File

Structure

92 AMD Geode™ SC1200/SC1201 Processor Data Book