TSS463B datasheet(38/59 Pages) ATMEL

38 / 59 page

TSS463B

4102E–AUTO–12/04

Identifier Tag and Command

Registers

The identifier tag and command registers are located at the base_address and

base_address + 1. It allows the user to specify the full 12-bit identifier field of the ISO

standard and the 4-bit command.

•

Read/Write registers.

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

rewritten with the identifier bits actually received.

EXT, RAK, RNW and RTR

(See Section “Message Types”, page 44). 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 that of the origi-

nally 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:

Only 1 level of link is supported.

654

321

ID_T 3

ID_T 2

ID_T 1

ID_T 0

EXT

RAK

RNW

RTR

base_address

+ 0x01

654

321

ID_T 11

ID_T 10

ID_T 9

ID_T 8

ID_T 7

ID_T 6

ID_T 5

ID_T 4

base_address

+ 0x00

654

321

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

TSS463B Datasheet(PDF) 38 Page - ATMEL Corporation

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