DS2155 datasheet(116/262 Pages) DALLAS

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DS2156

116 of 262

20.

T1 BIT-ORIENTED CODE (BOC) CONTROLLER

The DS2156 contains a BOC generator on the transmit side and a BOC detector on the receive side. The

BOC function is available only in T1 mode.

20.1 Transmit BOC

Bits 0 to 5 in the TFDL register contain the BOC message to be transmitted. Setting BOCC.0 = 1 causes

the transmit BOC controller to immediately begin inserting the BOC sequence into the FDL bit position.

The transmit BOC controller automatically provides the abort sequence. BOC messages are transmitted as

long as BOCC.0 is set.

Transmit a BOC

1) Write 6-bit code into the TFDL register.

2) Set the SBOC bit in BOCC = 1.

20.2 Receive BOC

The receive BOC function is enabled by setting BOCC.4 = 1. The RFDL register now operates as the

receive BOC message and information register. The lower six bits of the RFDL register (BOC message

bits) are preset to all 1s. When the BOC bits change state, the BOC change-of-state indicator, SR8.0,

alerts the host. The host then reads the RFDL register to get the BOC status and message. A change-of-

state occurs when either a new BOC code has been present for a time determined by the receive BOC

filter bits RBF0 and RBF1 in the BOCC register, or a nonvalid code is being received.

Receive a BOC

1) Set integration time through BOCC.1 and BOCC.2.

2) Enable the receive BOC function (BOCC.4 = 1).

3) Enable interrupt (IMR8.0 = 1).

4) Wait for interrupt to occur.

5) Read the RFDL register.

6) If SR2.7 = 1, then a valid BOC message was received.

– The lower six bits of the RFDL register comprise the message.

DS2155 Datasheet(PDF) 116 Page - Dallas Semiconductor