AMD Am79C930 Functional Description, Basic Functions, Detailed Functions, Bus Interface Unit

AMD		P R E L I M I N A R Y
		LLOCKE/	LLOCKE/
PCMCIA	LLOCKEN	SA15 Pin	SA15 Pin
Pin Value	TCR14[6]	Direction	Value
0	X	I	NA	(SA15 input function)
1	0	I	NA
1	1	O	TIR11[4]

FUNCTIONAL DESCRIPTION

Basic Functions

System Bus Interface Function

The Am79C930 device is designed with a choice of two system bus interfaces. The system designer may choose between the PCMCIA bus and the ISA (IEEE P996) bus with support for Plug and Play. Both inter- faces support an 8-bit wide data bus. The system inter- face is used by the host driver software to initialize the Am79C930 device through a series of slave I/O ac- cesses to the Am79C930 device. Device operation is monitored by accessing Am79C930 registers through the system bus interface. Network data is transferred to/from the driver through slave memory accesses at the system bus interface. Network data is stored in the SRAM that accompanies a complete Am79C930- based design.

Memory Bus Interface Function

The Am79C930 device contains a memory bus inter- face, which is used by the Am79C930 device to gain ac- cess to Flash memory for fetching 80188 instructions and to gain access to SRAM for fetching and storing driver commands, network data, and for temporary vari- able storage. Software driver transfers of network data are passed to the Am79C930 device through the system bus interface and will be automatically rerouted to the memory bus interface in order to reach the SRAM.

Software Interface Function

The software interface to the Am79C930 consists of a set of 256K memory locations and 16 (or 40) I/O loca- tions. 128K of these memory locations map directly to an SRAM that is attached to the memory interface. An- other 128K maps to a Flash memory device. Due to overlapping address space as viewed by the 80188 embedded processor core, 128 bytes of the SRAM space are not usable for driver function. Additional registers exist in the Am79C930 device for use by industry standard PCMCIA and ISA Plug and Play configuration utilities.

Network Interface Function

The Am79C930 device can be connected to an IEEE

802.11(draft) network via a flexible network interface. The flexible network interface allows the user to define much of the pin functionality in order to assist in accom- modating the Am79C930 device to a number of different network transceivers. Pin control is achieved through Transceiver Attachment Interface (TAI) registers (TIR

and TCR). These registers are controlled through 80188 firmware instructions.

Detailed Functions

Block Level Description

Bus Interface Unit

The Bus Interface Unit (BIU) supports either of two com- mon interfaces: PCMCIA and ISA (IEEE P996) with Plug and Play. The choice of interface is determined through a pin strapping option via the PCMCIA pin.

Two sets of command and status registers exist within the BIU. One set of registers is labeled System Interface Registers (SIR). The SIR registers are used to control the general function of the device by providing various resets and by allowing some direct communication be- tween the host system and the embedded 80188. The SIR registers are visible to the system interface, but are not visible to the 80188 embedded core. The second set of BIU registers is the MAC Interface Registers (MIR). The MIR registers are visible to the 80188 embedded core, but are not visible from the system interface. Some commands within each register set allow indirect communication between the system interface and the 80188 core.

Another set of registers is located in the Transceiver At- tachment Interface Unit, the TIR registers. The TIR loca- tions are visible through the BIU. These registers are normally used by the 80188 core to control the Trans- ceiver function; they are visible through the system interface primarily for diagnostic purposes.

The PCMCIA Card Configuration Registers and the set of ISA Plug and Play registers are implemented in the BIU. PCMCIA Card Information Structure and the ISA Plug and Play Resource Data area are both mapped to Flash space and are accessible through the system interface of the BIU.

All Am79C930 registers are located in I/O space as viewed from the system interface. There are no memory resources located inside of the BIU unit, although there are memory resources that are accessed through the BIU. For a complete description of all resources accessible inside of and through the BIU, see the Soft- ware Access section.

For a complete description of all resources accessible by the embedded 80188 processor, see the 80188 Firmware section.

42 Am79C930