80220 Datasheet, PDF (30/91 Pages) LSI Computer Systems – 100BASE-TX/10BASE-T Ethernet Media Interface Adapter

80220/80221
3.26.5 Frame Structure
The structure of the serial port frame is shown in Table 8
and a timing diagram of a frame is shown in Figure 9. Each
serial port access cycle consists of 32 bits (or 192 bits if
multiple register access is enabled and
REGAD[4:0]=11111), exclusive of idle. The first 16 bits of
the serial port cycle are always write bits and are used for
addressing. The last 16/176 bits are from one/all of the
11 data registers.
The first 2 bits in Table 8 and Figure 9 are start bits and
need to be written as a 01 for the serial port cycle to
continue. The next 2 bits are a read and write bit which
determine if the accessed data register bits will be read or
write. The next 5 bits are device addresses and they must
match the inverted values latched in from pins MDA[4:0]
during the power-on reset time for the serial port access to
continue. The next 5 bits are register address select bits
which select one of the five data registers for access. The
next 1 bit is a turnaround bit which is not an actual register
bit but extra time to switch MDIO from write to read if
necessary, as shown in Figure 2. The final 16 bits of the
MI serial port cycle (or 176 bits if multiple register access
is enabled and REGAD[4:0]=11111) come from the spe-
cific data register designated by the register address bits
REGAD[4:0].
3.26.6 Register Structure
The 80220/80221 has eleven internal 16 bit registers. Ten
registers are available for setting configuration inputs and
reading status outputs, and one register is reserved for
factory use. A map of the registers is shown in Table 9.
The ten accessible registers consist of six registers that
are defined by IEEE 802.3 specifications (Registers 0-5)
and four registers that are unique to the 80220/80221
(Registers 16-19).
The structure and bit definition of the Control register is
shown in Table 10. This register stores various configura-
tion inputs and its bit definition complies with the IEEE
802.3 specifications.
The structure and bit definition of the Status register is
shown in Table 11. This register contains device capabili-
ties and status output information. and its bit definition
complies with the IEEE 802.3 specifications.
The structure and bit definition of the PHY ID #1 and #2
registers is shown in Tables 12 and 13, respectively.
These registers contain an identification code unique to
the 80220/80221 and their bit definition complies with the
IEEE 802.3 specifications.
The structure and bit definition of the AutoNegotiation
Advertisement and AutoNegotiation Remote End Capabil-
ity registers is shown in Tables 14 and 15, respectively.
These registers are used by the AutoNegotiation algorithm
and their bit definition complies with the IEEE 802.3
specifications.
The structure and bit definition of the Configuration 1 and
Configuration 2 registers is shown in Table 16 and 17,
respectively. These registers store various configuration
inputs.
The structure and bit definition of the Status Output regis-
ter is shown in Table 18. This register contains output
status information.
The structure and bit definition of the Mask register is
shown in Table 19. This register allows each R/LT bit in the
Status Output register to be masked out or removed as a
bit that will set interrupt.
Register 20 is reserved for factory use. All bit values must
be set to the defaults for normal operation.
3.26.7 Interrupt
The 80220/80221 has hardware and software interrupt
capability. The interrupt is triggered by certain output
status bits (also referred to as interrupt bits) in the serial
port. As indicated previously, R/LT bits are read bits that
latch on transition. R/LT bits are also interrupt bits if they
are not masked out with the Mask register bits. Interrupt
bits automatically latch themselves into their register loca-
tions and assert the interrupt indication when they change
state. Interrupt bits stay latched until they are read. When
interrupt bits are read, the interrupt indication is deasserted
and the interrupt bits that caused the interrupt to happen
are updated to their current value. Each interrupt bit can
be individually masked and subsequently be removed as
an interrupt bit by setting the appropriate mask register bits
in the Mask register.
Interrupt indication is done in three ways: (1) MDINT pin,
(2) INT bit in the MI serial port Status Output register, and
(3) interrupt pulse on MDIO. The MDINT pin is an active
low interrupt output indication. The INT bit is an active high
interrupt register bit that resides in the Status Output
register. The interrupt pulse on MDIO also indicates
interrupt and is available when the interrupt pulse select bit
is set in the MI serial port Configuration 2 register. When
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MD400159/E