Cirrus Logic CS8952 - Manual (Page 71)

CS8952
CrystalLAN™ 100BASE-X and 10BASE-T Transceiver 71
DS206F1
When the TCM pin is high on power-up or reset, the CLK25 pin may be used as a source for the
TX_CLK pin. When the TCM pin is floating on power-up or reset, TX_CLK must be supplied externally.
TX_CLK should have the following nominal frequency:
TX_EN - Transmit Enable. Input, Pin 43.
Asserted high to indicate valid data nibbles are present on TXD[3:0]. When BPALIGN is selected,
TX_EN must be pulled up to VDD_MII.
TX_ER/TXD4 - Transmit Error Encoding/Transmit Data 4. Input, Pin 38.
When high, TX_ER indicates to the CS8952 that a transmit error has occurred. If TX_ER is asserted
simultaneously with TX_EN in 100 Mb/s mode, the CS8952 will ignore the data on the TXD[3:0] pins
and transmit one or more 100 Mb/s HALT symbols in its place. In 10 Mb/s mode, TX_ER has no effect
on the transmitted data.
If BP4B5B or BPALIGN are set, TX_ER/TXD4 is used to transmit the most-significant bit of the five-bit
code group.
TXD[3:0] - Transmit Data. Input, Pins 47, 46, 45, and 44.
Transmit data input pins. For MII modes, nibble-wide data (synchronous to TX_CLK) must be presented
on pins TXD[3:0] when TX_EN is asserted high. TXD0 is the least significant bit. In 10 Mb/s serial
mode, pin TXD0 is used as the serial input pin, and TXD[3:1] are ignored.
When either BP4B5B or BPALIGN is selected, pin TXD4 contains the most significant bit of the five-bit
code-group.
Control and Status Pins
10BT_SER - 10 Mb/s Serial Mode Select. Input, Pin 23.
When asserted high during power-up or reset and 10 Mb/s operation is selected, serial data will be
transferred on pins RXD0 and TXD0. When low during power-up or reset and 10 Mb/s operation is
selected, data is transferred a nibble at a time on RXD[3:0] and TXD[3:0]. This pin is ignored during
100 Mb/s operation.
10 Mb/s serial mode may also be entered under software control through bit 9 of the 10BASE-T Status
Register (address 1Bh).
At power-up or at reset, the value on this pin is latched into bit 9 of the 10BASE-T Status Register
(address 1Bh). This pin includes a weak internal pull-down (> 20 k
Ω), or the value may be set by an
external 4.7 k Ω pull-up or pull-down resistor.
AN[1:0] - Auto-Negotiate Control. Input, Pins 58 and 57.
These three-level input pins are sampled during power-up or reset. They control the forced or
advertised auto-negotiation operating modes. If one of these pins is left unconnected, internal logic pulls
its signal to a mid-range value, 'M'.
Speed 10BT_SER pin Nominal frequency
100 Mb/s n/a 25 MHz
10 Mb/s low (parallel) 2.5 MHz
10 Mb/s high (serial) 10 MHz
AN1 pin AN0 pin Speed Forced/Auto Full/Half Duplex
0 M 10 Mb/s Forced Half