Sundance Spas ST201 manual Maxlat

Sundance Technology		ST201
MAXLAT
Class	PCI Configuration Registers, Configuration
Base Address	PCI device configuration header start
Address Offset	0x3f
Access Mode	Read Only
Width	8 bits

PRELIMINARY draft 2

BIT

7..0

BIT NAME

MaxLat

BIT DESCRIPTION

MaxLat specifies, in 250 ns increments, how often the ST201 requires bus access while operating as a bus master. The value for MaxLat is stored in the ConfigParm word in EEPROM. Assumes the PCI system allows 64-byte maximum bursts with full duplex operation, the ST201- based 100 Mbps systems return the value 10 in this field, implying a latency tolerance of 2.5us, according to the calculation:

64 bytes/(12.5 MB/s x 2) = 2.56us

The result is rounded to 2.5 us, which is 250 ns * 10

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