Firmware

AN2282

10/19

The inb function is used only to perform the switch of Ethernet controller from an 8-bit to a

16-bit data interface because, even if after a reset the CS8900A starts in 8-bit mode, it is

recommended to be used in 16-bit mode. This switching operation is done by driving a

transition on nSBHE pin of CS8900A, so connecting this pin to address line SA0 (see

Figure 2), the transition is simply done by performing some dummy byte read operations.

2.1.2

Initialization and configuration

The lan8900.c module provides all the functions for CS8900A initialization, configuration

and packet transmission/reception management. The Ethernet controller can be initialized

either by using an external EEPROM (where all configuration words are automatically

downloaded into the CS8900A internal registers at reset time) or by filling them through

software. In this application note the Ethernet controller is initialized and configured by the

function

●

unsigned long csInitFromBSPDefs(void);

This function reads the configuration constant from the module bsp.h. The header file for

this is mainly defined as follows:

a)

The base address for I/O access mode:

#define BSP_CS8900_IO_BASE

0x300

b)

The interrupt request number:

#define BSP_CS8900_IRQ

10

This number defines which interrupt line of the Ethernet Controller must be

connected to the external interrupt line of the STR7 [5].

c)

The access type (I/O or memory mode):

#define BSP_CS8900_MEM_MODE

YES

d)

The base address for memory access mode:

#define BSP_CS8900_MEM_BASE

0x01000

e)

The media type:

#define BSP_CS8900_MEDIA_TYPE

TEN_BASE_T

f)

The individual Ethernet address:

#define BSP_CS8900_IND_ADDR

"00:24:20:10:FF:41"

The header file lan8900.h defines all CS8900A internal registers, for more details refer to

the CS8900A datasheet. All Initialization functions (csInitFromBSPDefs included) are called

by the function:

●

unsigned long csInitialize( void (*ap_addr)(mblk_t *, IA, IA) );

The function verifies the Ethernet controller ID and resets it by calling the following

functions:

●

unsigned long csVerifyChip(void);

●

unsigned long csResetChip(void);

Moreover, this function sets the individual and broadcast Ethernet addresses, the function

for new packet notification from the passed argument and initializes the interrupt number

calling the function unsigned long csInitInterrupt(void);

2.1.3

Ethernet packet management

The packets to transmit or to receive are exchanged with the upper layer as messages with

the following structure: