AMD SC1200 IDE Controller, Video Retrace Interrupt, IDE Configuration Registers, PIO Mode, 144

32579B Core Logic Module

6.2.2.1Video Retrace Interrupt

Bit 7 of the “Serial Packet” can be used to generate an SMI whenever a video retrace occurs within the GX1 module. This function is normally not used for power management but for SoftVGA routines. Setting F0 Index 83h[2] = 1 enables this function. A read only status register located at F1BAR0+I/O Offset 00h[5] can be read to see if the SMI was caused by a video retrace event.

6.2.3IDE Controller

The Core Logic module integrates a PCI bus mastering, ATA-4 compatible IDE controller. This controller supports UltraDMA, Multiword DMA and Programmed I/O (PIO) modes. Two devices are supported on the IDE controller. The data-transfer speed for each device can be indepen- dently programmed. This allows high-speed IDE peripher- als to coexist on the same channel as lower speed devices.

The Core Logic module supports two IDE channels, a pri- mary channel and a secondary channel.

The IDE interface provides a variety of features to optimize system performance, including 32-bit disk access, post write buffers, bus master, Multiword DMA, look-ahead read buffer, and prefetch mechanism for each channel respec- tively.

The IDE interface timing is completely programmable. Tim- ing control covers the command active and recover pulse widths, and command block register accesses. The IDE data-transfer speed for each device on each channel can be independently programmed allowing high-speed IDE peripherals to coexist on the same channel as older, com- patible devices.

The Core Logic module also provides a software accessi- ble buffered reset signal to the IDE drive, F0 Index 44h[2]. The IDE_RST# signal can be driven low or high as needed for device-power-off conditions. IDE_RST# is not driven low by POR# (Power-On Reset).

6.2.3.1IDE Configuration Registers

Registers for configuring Channels 0 and 1 are located in the PCI register space designated as Function 2 (F2 Index 40h-5Ch). Table 6-35 on page 256 provides the bit formats for these registers. The IDE bus master configuration regis- ters are accessed via F2 Index 20h which is Base Address Register 4 in Function 2 (F2BAR4). See Table 6-36 on page 260 for register/bit formats.

The following subsections discuss Core Logic operational/ programming details concerning PIO, Bus Master, and UltraDMA/33 modes.

6.2.3.2PIO Mode

The IDE data port transaction latency consists of address latency, asserted latency and recovery latency. Address latency occurs when a PCI master cycle targeting the IDE data port is decoded, and the IDE_ADDR[2:0] and IDE_CS# lines are not set up. Address latency provides the setup time for the IDE_ADDR[2:0] and IDE_CS# lines prior to IDE_IOR# and IDE_IOW#.

Asserted latency consists of the I/O command strobe assertion length and recovery time. Recovery time is pro- vided so that transactions may occur back-to-back on the IDE interface without violating minimum cycle periods for the IDE interface.

If IDE_IORDY is asserted when the initial sample point is reached, no wait states are added to the command strobe assertion length. If IDE_IORDY is negated when the initial sample point is reached, additional wait states are added.

Recovery latency occurs after the IDE data port transac- tions have completed. It provides hold time on the IDE_ADDR[2:0] and IDE_CS# lines with respect to the read and write strobes (IDE_IOR# and IDE_IOW#).

The PIO portion of the IDE registers is enabled through:

•Channel 0 Drive 0 Programmed I/O Register (F2 Index 40h)

•Channel 0 Drive 1 Programmed I/O Register (F2 Index 48h)

•Channel 1 Drive 0 Programmed I/O Register (F2 Index 50h)

•Channel 1 Drive 1 Programmed I/O Register (F2 Index 58h)

The IDE channels and devices can be individually pro- grammed to select the proper address setup time, asserted time, and recovery time.

The bit formats for these registers are shown in Table 6-35 on page 256. Note that there are different bit formats for each of the PIO programming registers depending on the operating format selected: Format 0 or Format 1:

•F2 Index 44h[31] (Channel 0 Drive 0 — DMA Control Register) sets the format of the PIO register.

—If bit 31 = 0, Format 0 is used and it selects the slowest PIO mode (bits [19:16]) per channel for commands.

—If bit 31 = 1, Format 1 is used and it allows indepen- dent control of command and data.

Also listed in the bit formats are recommended values for the different PIO modes. Note that these are only recom- mended settings and are not 100% tested.

When using independent control of command and data cycles the following algorithm should be used when two IDE devices are sharing the same channel:

1)The PIO data cycle timing for a particular device can be the timing value for the maximum PIO mode which that device reports it supports.

2)The PIO command cycle timing for a particular device must be the timing value for the lowest PIO mode for both devices on the channel.

144 AMD Geode™ SC1200/SC1201 Processor Data Book