T8538B 查看數據表（PDF） - Agere -> LSI Corporation

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T8538B

Quad Programmable Codec

Agere -> LSI Corporation 

T8538B Quad Programmable Codec

Preliminary Data Sheet

August 2001

Functional Description (continued)

The Control Interface (continued)

Protocol

The format of the command protocol is shown in Fig-

ures 4 and 5.

The control interface operates with one external master

controller and multiple slave codec devices. Each

transfer is initiated by the master, and the slave

responds for either read operations or the fast scan

mode. The slave does not check the bus for activity

prior to transmitting; it only checks for an active CS.

The master should allow for a wait between the end of

a read command until CS becomes active for the read

data. The master must refrain from sending additional

commands to the slave chip until the response is

received. On a 4-wire bus, commands to other devices

may be initiated before the response is received, but

care in generating the CS function is needed to ensure

that the multiple responses do not interfere. It should

be noted that multiple memory locations can be

accessed in the same command by setting the data

field length field to the desired number of bytes to be

transferred. If flow control is desired, it must be per-

formed by using separate commands, each transfer-

ring smaller blocks of information, or by controlling the

serial clock (gapping the serial clock), or with CS in the

case of byte-by-byte mode.

There is no response from the slave to the master for a

write operation. The response to a read operation sim-

ply includes the data to be read in the data field. Com-

mands from the master controller include data for write

operations, but not for read operations.

All data is transmitted in a byte-oriented fashion with

the least significant bit of each byte transferred first.

Multibyte fields are transferred least significant byte

first in both directions. The data field will contain the

first addressed data location first, with subsequent data

locations transmitted in ascending order.

Since the coefficients and gains are stored in volatile

memory, all the coefficients and gains must be loaded

after powerup. There is, however, no need to reload

them when switching from active to standby modes, or

vice versa.

10

Agere Systems Inc.

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