TSS461C datasheet(36/57 Pages) ATMEL

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TSS461C

4193G–AUTO–12/04

ID_T [11:0]: Identifier Tag

Upon a reception hit (i.e, a good comparison between the identifier received and an

identifier specified, taking the comparison mask into account, as well as a status and

command indicating a message to be received, the identifier tag bits value will be rewrit-

ten with the identifier bits actually received.

EXT, RAK, RNW & RTR: (See

Section “Retries, Rearbitrate

and Abort”)

No comparison will be done on the command bits, except on EXT bit. The RAK, RNW

and RTR bits will be written into the first byte of the Message upon a reception hit.

The RNW and RTR bits, as well as the status bits in the length and status register, must

be in a valid position for reception or transmission. If not, the message corresponding to

this identifier is considered as inactive or invalid.

The way of knowing if an acknowledge sequence was requested or not is to check the

first byte of the Message.

Message Pointer Register

The message pointer register at address (base_address + 0x02) is 8 bits wide. It indi-

cates where, in the Message DATA RAM area, the message buffer is located.

•

Read/Write register

DRAK: Disable RAK (Used in

'Spy Mode')

In reception: whatever is the RAK bit of the incoming valid frame, no ACK answer will be

set. If the message was successfully received, an IT is set (ROK or RNOK).

In transmission: no action.

One: disable active, 'spy' mode.

Zero: disable inactive, normal operation.

M_P [6:0]: Message Pointer

Since the Message DATA RAM area base address is 0x80, the value in this register is

the offset from that address. If the message buffer length value is illegal (i.e. zero), this

channel that contains the actual message pointer, message length and received status.

However, the identifier, mask, error and transmitted status used will be the originally

matched channel. In any case, if a link is intended, the three high bits of M_P [6:0]

should be set to 0.

This allows several channels to use the same actual reception buffer in Message DATA

RAM, thus diminishing the memory usage.

Note that only 1 level of link is supported.

76543210

DRAK

M_P 6

M_P 5

M_P 4

M_P 3

M_P 2

M_P 1

M_P 0

base_address

+ 0x02

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