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AIC-6915 Ethernet LAN Controller Programmer’s Manual
Terminology
Throughout this chapter, data values are defined as follows:
■
Byte = 8 bits
■
Halfword = 16 bits
■
Word = 32 bits
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Doubleword = 64 bits
AIC-6915 Internal Registers
These registers are used by the software driver for configuration, control, and retrieval of
status information. All registers which are ‘cleared on read’ are reset when the most
significant bit is read. Reading any other byte in a byte or halfword operation does not
affect the register. When the AIC-6915 activates a function as a result of writing to a
register, the activation takes place (usually) when writing the most-significant-byte of the
register.
All registers ‘Byte Address’ is defined as the offset byte address from the start of the
memory space dedicated for internal registers - 0x50000h.
Reserved fields are always read as zero. Values written to reserved fields are ignored.
However, the host should always write a zero to reserved fields to ensure compatibility
with future versions of the AIC-6915 that might use these fields.
Regions in the memory map that do not contain registers may be read as any value.
Writing to them has no effect.
Certain bits of certain registers in the AIC-6915 are not directly accessible by software and
are cleared by writing a logic one to the bit. These bits are originally set (written as a 1) by
the AIC-6915 based on an event or condition. Software can read the status of these
registers to determine the appropriate course of action. Software clears the bit by writing a
logical one to the logic block that manages the register. The logic block is in turn
responsible for setting the actual bit to zero.
The Reset Value column of each register is the value of the bit after a power-up or reset
cycle.
