CP2201 datasheet(78/108 Pages) SILABS

78 / 108 page

CP2200/1

Rev. 1.0

14. Media Access Controller (MAC)

The CP2200/1 has an IEEE 802.3 compliant Ethernet Media Access Controller (MAC). The MAC can be

configured to automatically pad short frames (full duplex mode only), append CRC, and perform frame length

checking. A loopback mode separate from PHY loopback is also provided for system debugging. The MAC is

configured through nine indirect 16-bit registers summarized in Table 20.

14.1. Initializing the MAC

MAC initialization occurs after the physical layer initialization and typically occurs once after each reset or Auto-

Negotiation Complete interrupt. Most MAC indirect registers can be left at their reset values. See “6.2. Reset

Initialization” on page 18 for the complete reset initialization procedure. The following are the steps required to

initialize the MAC:

Step 1: Determine if the physical layer is set to full-duplex or half-duplex. The MAC must be set to the same

duplex mode as the physical layer before sending or receiving any packets.

Step 2: Write 0x40B3 (full-duplex) or 0x4012 (half-duplex) to MACCF. The appropriate bits in this register

may also be set or cleared to change padding options or MAC behavior.

Step 3: Write 0x0015 (full-duplex) or 0x0012 (half-duplex) to IPGT.

Step 4: Write 0x0C12 to IPGR.

Step 5: Write 0x05EE to MAXLEN.

Step 6: Program the 48-bit Ethernet MAC Address by writing to MACAD0:MACAD1:MACAD2.

Step 7: Write 0x0001 to MACCN to enable reception. If loopback mode or flow control is desired, set the

appropriate bits to enable these functions.

14.2. Accessing the Indirect MAC Registers

The indirect MAC registers are accessed through four direct mapped registers: MACADDR, MACDATAH,

MACDATAL, and MACRW. The MAC registers can be accessed using the following procedure:

Step 1: Write the address of the indirect register to MACADDR.

Step 2: If writing a value to the indirect register, write a 16-bit value to MACDATAH:MACDATAL.

Step 3: Write any value to MACRW to transfer the contents of MACDATAH:MACDATAL to the indirect

Step 4: Perform a read on MACRW to transfer the contents of the indirect register to

MACDATAH:MACDATAL. The MACDATAH and MACDATAL registers may now be directly read to

determine the contents of the indirect register.

CP2201 Datasheet(PDF) 78 Page - Silicon Laboratories