AMD Am79C930 manual USER7, Adref, Sdclk, Sddata

P R E L I M I N A R Y AMD

TXMOD

Transmit Modulation Enable Output

TXMOD is an active low output that is used to enable the transmit modulation function of the attached trans- ceiver. This pin is directly controlled by the transmit state machine in the TAI and the TXMOD bit of TIR11. The timing of the TXMOD signal is programmable from a TAI register. The polarity of this pin is programmable from a TAI register.

TXPE

Transmit Power Enable Output

TXPE is an active low output that is used to enable the transceiver's transmission amplifier. When TXPE is low, the transceiver should enable its transmission amplifier. When TXPE is high, the transceiver should disable its transmission amplifier. This pin is directly controlled by the transmit state machine in the TAI and the TXPE bit of the TIR11. The timing of the TXMOD signal is program- mable from a TAI register. The polarity of this pin is pro- grammable from a TAI register.

USER7

USER7 Input/Output

USER7 is a pin that may be directly controlled through TIR and TCR register locations.

Other Pins

ACT

Activity LED Output

ACT is an active low open collector output that is directly controllable through a TAI register. This pin is capable of sinking the 12 mA necessary to drive a typical indicator LED. This pin is directly controllable through a TAI regis- ter and is also programmable as an I/O with read capa- bility. This pin may also be programmed to actively drive high output values. When an LED is connected to this pin, then proper operation of this output requires a pull-up device to be connected externally.

ADREF

A/D Reference Input

ADREF is a single-ended analog input that is used by the A/D conversion circuit. ADREF is the reference volt- age that is fed to the resistor ladder of the D/A portion of the A/D circuit. ADREF is used to determine the range of sensitivity of the A/D circuit. The recommended value for ADREF is 1.25 to 1.75 V. Note that ADREF is volt- age-doubled before being used for internal A/D refer- ence. For example, an ADREF value of 1.75 V will mean that the A/D will give a max digital output value for an ADIN input of 3.5 V or higher.

ADIN[1–2]

A/D sample inputs Input/Output

ADIN[1–2] are inputs that accept single-ended analog input values for conversion by the internal Am79C930

A/D converter. Only one input will be sampled at any time for conversion by the internal Am79C930 device's A/D circuit. The input that will be converted by the A/D circuit is determined by the setting of the SRCS bit of the Antenna Diversity and A/D Control register in the TAI (TIR26).

LNK

Link LED Output

LNK is an active low open collector output that is directly controllable through a TAI register. This pin is capable of sinking the 12 mA necessary to drive a typical indicator LED. This pin is directly controllable through a TAI regis- ter and is also programmable as an I/O with read capa- bility. This pin may also be programmed to actively drive high output values. When an LED is connected to this pin, then proper operation of this output requires a pull-up device to be connected externally.

PWRDWN

Powerdown Output

PWRDWN is an output that becomes active (HIGH) when the Am79C930 device enters the power down mode. This pin can be used to power down other sec- tions of a Am79C930-based system design.

SAR[6–0]

Serial Approximation Register Input/Output

SAR[6–0] are outputs that are used to deliver the value of the internal A/D converter for use external to the Am79C930 device. These pins are directly controllable through a TAI register and are also programmable as I/O pins with read capability.

SDCLK

Serial Device Clock Output

SDCLK is an output that is used to clock data on the SDDATA output pin. This pin may be used in combina- tion with the SDDATA and SDSEL output pins in order to create an I2C serial device interface. This pin is directly controllable through a TAI register and is also program- mable as an I/O with read capability.

SDDATA

Serial Device Data Input/Output

SDDATA is an I/O pin that may be used in conjunction with the SDCLK and SDSEL pins in order to create an I2C serial device interface. This pin is directly controlla- ble through a TAI register and is also programmable as an I/O with read capability.

SDSEL[1–3]

Serial Device Select Output

SDSEL[1–3] are output pins that may be used in con- junction with the SDCLK and SDSEL pins in order to cre-

ate an I2C serial device interface. These pins are directly controllable through a TAI register and are also pro- grammable as I/O pins with read capability.

Am79C930 31