DS2155 datasheet(116/238 Pages) DALLAS

116 / 238 page

DS2155

116 of 238

22.3 Method 3: Internal Register Scheme Based on CRC4 Multiframe

The receive side contains a set of eight registers (RSiAF, RSiNAF, RRA, and RSa4–RSa8) that report the

Si and Sa bits as they are received. These registers are updated with the setting of the receive CRC4

multiframe bit in Status Register 2 (SR4.1). The host can use the SR4.1 bit to know when to read these

registers. The user has 2ms to retrieve the data before it is lost. The MSB of each register is the first

received. See the following register descriptions for more details.

The transmit side also contains a set of eight registers (TSiAF, TSiNAF, TRA, and TSa4–TSa8) that,

through the transmit Sa bit control register (TSaCR), can be programmed to insert Si and Sa data. Data is

sampled from these registers with the setting of the transmit multiframe bit in Status Register 2 (SR4.4).

The host can use the SR4.4 bit to know when to update these registers. It has 2ms to update the data or

else the old data is retransmitted. The MSB of each register is the first bit transmitted. See the following

RSiAF

Received Si Bits of the Align Frame

C8h

Bit #

Name

SiF0

SiF2

SiF4

SiF6

SiF8

SiF10

SiF12

SiF14

Default

Bit 0/Si Bit of Frame 14 (SiF14)

Bit 1/Si Bit of Frame 12 (SiF12)

Bit 2/Si Bit of Frame 10 (SiF10)

Bit 3/Si Bit of Frame 8 (SiF8)

Bit 4/Si Bit of Frame 6 (SiF6)

Bit 5/Si Bit of Frame 4 (SiF4)

Bit 6/Si Bit of Frame 2 (SiF2)

Bit 7/Si Bit of Frame 0 (SiF0)

DS2155 Datasheet(PDF) 116 Page - Dallas Semiconductor