Intel® 41210 Serial to Parallel PCI Bridge Developer’s Manual 93

Register Description
12.2.28 Offset 4Ch: EXP_DCTL—PCI Express* Device Control
Register

This register stores command bits that control the 41210 behavior on PCI Express*.

Table 62. Offset 4Ch: EXP_DCTL—PCI Express* Device Control Register (Sheet 1 of 2)

Bits Type Default Description
15 RW 0b
Bridge Configuration Retry Enable: When set, the bridge is enabled to return a
completion with Completion Retry Status (CRS) on PCI Express* when a configuration
transaction to the secondary interface did not complete within the PCI completion time-out
period.
14:12 RW 010b
Max_Read_Request_Size: This field applies to the bridge segment when the segment is in
PCI mode only. When in PCI-X mode, this field does not apply. The Intel® 41210 Serial to
Parallel PCI Bridge cannot send requests larger than the size indicated by this field.
Encodings are as follows:
11 RO 0b Enable No Snoop: Hard-wired to 0
10 RO 0b Auxiliary (AUX) Power PM Enable: Not supported
9RO 0b
Phantom Function Enable: Not supported
8RO 0b
Extended Tag Field Enable: Ignored because only 5-bit tag is supported
7:5 RW 000b
Maximum Payload Size: These bits indicate the maximum payload size supported for
TLPs. Supported encodings are as follows:
All other values default to 128 bytes.
4RO 0b
Enable Relaxed Ordering: Hard-wired to 0
3RW 0b
Unsupported Request Reporting Enable: This bit controls the enabling of
ERR_NONFATAL or ERR_FATAL messages on PCI Express* for reporting “Unsupported
Request” errors. Note that the following requests use this enable bit:
• requests from PCI Express* that are unsupport ed
• requests from PCI Express* that master-abor t on the internal switch
Bit Max_Read_Request_Size
000b 128-byte maximum read request size
001b 256-byte maximum read request size
010b 512-byte maximum read request size
011b 1024-byte maximum read request size
100b 2048-byte maximum read reques t size
101b 4096-byte maximum read reques t size
110b Reserved (the 41210 defaults to 512 bytes)
111b Reserved (the 41210 defaults to 512 bytes)
Bit Max_Payload_Size
000b 128-byte max imum payload size
001b 256-byte max imum payload size