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Am79C976
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P R E L I M I N A R Y
AUTOPOLL4:
Auto-Poll4 Register
Offset 090h
This register controls the automatic polling of a user-
selectable external PHY register, AP_REG4.
All bits in this register are set to their default values by
H_RESET. All bits are also set to their default values
before EEPROM data are loaded or after an EEPROM
read failure.
The default value for all bits in this register is 0.
Table 36. AUTOPOLL4: Auto-Poll4 Register
Bit
Name
Description
15
AP_REG4_EN
Enable Bit for Autopoll Register 4. When this bit and the Auto-Poll External PHY bit (APEP) in
CMD1 are both set to 1, the Auto-Poll State Machine periodically reads the external PHY register
selected by the AP_PHY4_ADDR and AP_REG4_ADDR fields and sets the APINT4 interrupt bit
if it detects a change in the register
’
s contents.
14-13
RES
Reserved locations. Written as zeros and read as undefined.
12-8
AP_REG4_ADDR
AP_REG4 Address. This field contains the register number of an external PHY register that the
Auto-Poll State Machine will periodically read if the AP_REG4_EN bit in this register and the
APEP bit (CMD3, bit 24) is set.
7
RES
Reserved location. Written as zero and read as undefined.
6
AP_PRE_SUP4
Auto-Poll Preamble Suppression. If this bit is set to 1, the Auto-Poll State Machine will suppress
the preambles of the MII Management Frames that it uses to periodically read the external PHY
register selected by the AP_PHY4_ADDR and AP_REG4_ADDR fields.
This bit is ignored when the AP_PHY4_DFLT bit is set.
5
AP_PHY4_DFLT
Auto-Poll PHY4 Default. When this bit is set, the Auto-Poll State Machine ignores the contents of
the AP_PHY4_ADDR and AP_PRE_SUP4 fields and uses the AP_PHY0_ADDR field for the
address of the PHY device to be polled. If this bit is set, the Auto-Poll State Machine will suppress
preambles only if the Port Manager has determined that the default external PHY can accept MII
Management Frames without preambles. (The Port Manager examines bit 6 in register 1 of the
default PHY to make this determination.)
4-0
AP_PHY4_ADDR
Auto-Poll PHY4 Address. This field contains the address of the external PHY that contains
AP_REG4.
This bit is ignored when the AP_PHY4_DFLT bit is set.