AX88196BLF datasheet(28/86 Pages) ASIX

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ASIX ELECTRONICS CORPORATION

AX88196BLF

4.4.2 Half-Duplex Flow Control

Whenever the receive buffer becomes full crosses a certain threshold level, The MAC starts sending a Jam signal,

which will result in a collision. After sensing the collision, the remote station will back off its transmit ion.

AX88196B only generate this collision-based of back-pressure when it receives a new frame, in order to avoid any

late collisions.

A programmable of “Back-pressure Jam Limit count” (Offset 17h) is used for avoid HUB port partition due to many

continues of collisions. AX88196B will reset the “Back-pressure Jam Limit count” when either a transmitted or

received frame without collision. A back-pressure leakage allow when senses continue of collisions count up to

“Back-pressure Jam Limit count”, it will be no jamming one of receive frame even receive buffer is full.

4.5 Big- and Little-endian Support

AX88196B supports “Big-“ or “Little-endian” processor. To support big-endian processors, the hardware designer

must explicitly invert the layout of the byte lanes. In addition, for a 16-bit interface, the big-endian register must be

set correctly following the table below.

Additionally, please refer to Big-endian register (offset 1Eh), for additional information on status indication on big-

or little-endian modes.

MODE OFOPERATION AX88196B DATA PINS

DESCRIPTION

SD[15:8]

SD[7:0]

Mode 0 Big-endian register (offset 1Eh) not equal to 0x0000h

Even access

Byte3

Byte2

Odd access

Byte1

Byte0

This mode can be used by 32-bit processors

operating with an external 16-bit bus.

Mode 0 Little-endian register (offset 1Eh) equal to 0x0000h (default)

Even access

Byte1

Byte0

Odd access

Byte3

Byte2

This mode can also be used by native 16-bit

processors.

Tab - 12 Byte Lane Mapping

AX88196B’s 16-bit Data Port (DP) read/write like a FIFO not rely on address pin. The “Even access” means the

first of access Data Port (DP) behind of remote read/write Command Register (CR). The second time access Data

Port (DP) is “Odd access” and then next is “Even access”, and so on.

Host can read bit-7 in “Device Status Register” (Offset 17h) to know the current of big- or little-endian types. The

default is Little-endian mode.

4.6 General Purpose Timer (GP Timer)

The programmable General Purpose Timer can be used to generate periodic host interrupts and the resolution of this

timer is 100us.

The GP timer is a 16-bit of register. GPT1 (CR page3 offset 0Fh) and GPT0 (CR page3 offset 0Eh) to compost this

16-bit of General Purpose Timer. This GP timer field of default value is FFFFh. Once set the General Purpose

Timer Enable (CR page3 Offset 0Dh) the GPT counts down until it reaches 0000h then update the a new pre-load

value into GPT, and continues counting.

The GPT interrupt has no status indicate in Interrupt Status Register (CR page0 offset 07h). The interrupt event will

keep active until host driver read Interrupt Status Register (CR page0 offset 07h) then clear GPT interrupt event.

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