DS2155 datasheet(102/262 Pages) DALLAS

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DS2156

102 of 262

16.

PER-CHANNEL IDLE CODE GENERATION

Channel data can be replaced by an idle code on a per-channel basis in the transmit and receive

directions. When operated in the T1 mode, only the first 24 channels are used by the DS2156, the

remaining channels, CH25–CH32, are not used.

The DS2156 contains a 64-byte idle code array accessed by the idle array address register (IAAR) and the

per-channel idle code register (PCICR). The contents of the array contain the idle codes to be substituted

into the appropriate transmit or receive channels. This substitution can be enabled and disabled on a per-

channel basis by the transmit-channel idle code-enable registers (TCICE1–4) and receive-channel idle

code-enable registers (RCICE1–4).

To program idle codes, first select a channel by writing to the IAAR register. Then write the idle code to

the PCICR register. For successive writes there is no need to load the IAAR with the next consecutive

address. The IAAR register automatically increments after a write to the PCICR register. The auto

increment feature can be used for read operations as well. Bits 6 and 7 of the IAAR register can be used

to block write a common idle code to all transmit or receive positions in the array with a single write to

the PCICR register. Bits 6 and 7 of the IAAR register should not be used for read operations. TCICE1–4

and RCICE1–4 are used to enable idle code replacement on a per-channel basis.

Table 16-A. Idle-Code Array Address Mapping

BITS 0 to 5 OF IAAR

MAPS TO CHANNEL

Transmit Channel 1

Transmit Channel 2

Transmit Channel 3

—

Transmit Channel 31

Transmit Channel 32

Receive Channel 1

Receive Channel 2

Receive Channel 3

—

Receive Channel 31

Receive Channel 32

DS2155 Datasheet(PDF) 102 Page - Dallas Semiconductor