DS31256 datasheet(140/183 Pages) MAXIM

140 / 183 page

DS31256 256-Channel, High-Throughput HDLC Controller

140 of 183

PRCC0

PCI Revision ID/Class Code Register 0

0x008h

LSB

Revision ID (Read Only/Set to 00h)

Class Code (Read Only/Set to 00h)

Class Code (Read Only/Set to 80h)

MSB

Class Code (Read Only/Set to 02h)

Bits 0 to 7/Revision ID. These read-only bits identify the specific device revision, which is selected by Dallas

Semiconductor.

Bits 8 to 15/Class Code Interface. These read-only bits identify the subclass interface value for the device and

are fixed at 00h. See Appendix D of PCI Local Bus Specification Revision 2.1 for details.

Bits 16 to 23/Class Code Subclass. These read-only bits identify the subclass value for the device and are fixed at

80h, which indicate “Other Network Controller.” See Appendix D of PCI Local Bus Specification Revision 2.1 for

details.

Bits 24 to 31/Class Code Base Class. These read-only bits identify the base class value for the device and are

fixed at 02h, which indicate “Network Controllers.” See Appendix D of PCI Local Bus Specification Revision 2.1

for details.

PLTH0

PCI Latency Timer/Header Type Register 0

0x00Ch

LSB

Cache Line Size

Latency Timer

Header Type (Read Only/Set to 80h)

MSB

BIST (Read Only/Set to 00h)

Bits 0 to 7/Cache Line Size. These read/write bits indicate the cache line size in terms of dwords. If the burst size

of a data read transaction exceeds this value, the PCI block uses the memory read multiple command. Valid

settings are 04h (4 dwords), 08h, 10h, 20h, and 40h (64 dwords). Other settings are interpreted as 00h. These bits

are forced to 0 when a hardware reset is initiated through the

PRST pin.

Bits 8 to 15/Latency Timer. These read/write bits indicate the value of the latency timer (in terms of the number

of PCI clocks) for use when the device is a bus master. These bits are forced to 0 when a hardware reset is initiated

through the

PRST pin.

Bits 16 to 23/Header Type. These read-only bits are forced to 80h, which indicate a multifunction device.

Bits 24 to 31/Built-In Self-Test (BIST). These read only bits are forced to 0.

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