CP2201 datasheet(85/108 Pages) SILABS

85 / 108 page

CP2200/1

Rev. 1.0

Indirect Register 5. CWMAXR: Collision Window and Maximum Retransmit Register

Indirect Register 6. MAXLEN: Maximum Frame Length Register

Note: This register does not require initialization and will be left at its reset value by most systems.

Bits 15–14:Reserved. Read = 00b; Must write 00b.

Bits 13–8:CW: Collision Window

Sets the collision window in which collisions occur in a properly configured network.

The collision window is specified in the number of bytes from the start of transmission. The pream-

ble and frame delimiter are included in the byte count. Its default of 0x37 corresponds to the count

of frame bytes at the end of the window.

Bits 7–4: Reserved. Read = 0000b; Must write 0000b.

Bits 3–0: MAXR: Maximum Retransmit Attempts

Sets the maximum number of retransmit attempts following a collision before aborting the packet

due to excessive collisions. IEEE 802.3 specifies a maximum value of 0x0F (15d).

R/WR/W

R/W

Reserved

Bit15

Bit14

Bit13

Bit12

Bit11

Bit10

Bit9

Bit8

R/W

Default Value

Reserved

MAXR

0x370F

Bit7

Bit6

Bit5

Bit4

Bit3

Bit2

Bit1

Bit0

MACADDR:

0x04

Note: This register does not require initialization and will be left at its reset value will be set to 1518 (0x05EE)

by most systems.

Bits 15–0:MAXF: Maximum Frame Length

Specifies the maximum length of a receive frame. The default value is 0x600 (1536 octets). This

shorter frame lengths are untagged (1518 octets) and tagged (1522 octets). If a proprietary header

is allowed, this field should be adjusted accordingly.