QT2022/32 - Data Sheet: DS3051
9.6.3 Operation Code Field (OP)
The Operation Code field describes the major function of the frame. Four frame types are supported, correspond-
ing to the frames shown in figure 23 on page 76. The OP Codes for each frame type are shown in figure 33 on
page 77.
Table 33: OP Code Definitions
OP Code
Operation
00
01
11
10
Register Address
Write Data
Read Data
Post Read Data + Increment
9.6.4 Port Address Field (PRTAD)
The Port Address is five bits, allowing 32 unique port addresses.
The QT2022/32 port address is set through pins PRTAD<4:0>.
9.6.5 Device Address Field (DEVAD)
The Device Address is five bits, allowing 32 unique devices per port. The QT2022/32 supports device addresses 1
(PMA/PMD), 3 (PCS) and 4 (PHY XS).
9.6.6 Turnaround Field (TA)
The Turnaround time is a two bit time spacing between the Register Address field and the Data field of a manage-
ment frame to avoid contention during a read transaction.
9.6.7 Data/Address Field
The Data/Address field is 16 bits. For the “Register Address” frame, this field contains the register address. For all
other field types, it contains data. The first bit transmitted/received is bit 15, MSB, and the last bit is bit 0, LSB.
9.6.8 Idle Field (IDLE)
The IDLE condition on MDIO is a high-impedance state. The open drain driver will be turned off and the external
pull-up resistor will pull the MDIO line to a logic one.
9.7 XFP Module Access Through MDIO
In an XFP application, the I2C bus of the QT2022/32 can be connected to the XFP module. The chip can commu-
nicate with the XFP module using the same read/write control register and memory space as the XENPAK NVR
EEPROM defined in Section 10 on page 79. The XFP module I2C interface must be connected to the
EEPROM_SCL and EEPROM_SDA clock and data lines. The XFP module address is 1010000x. The 256 byte
XFP address space will be automatically read upon powerup or reset of the QT2022/32.
Read and write access to the XFP module uses the same register commands that apply to the EEPROM device.
The control register for read/write access is Register 1.8000h. The XFP address space will be mapped to the
QT2022/32 EEPROM memory space located in Register 1.8007-1.8106h.
When the QT2022/32 is in XFP mode any XENPAK interpretation of the address space is deactivated. For exam-
ple, no DOM access will be performed and DOM-related LASI alarms are not triggered.
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