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4.0 S-LINK Usage Instructions

4.4 Control/Data Bit

All words transmitted by the S-LINK are accompanied by a control/data bit which is carried on the lines UCTRL# and LCTRL#. This works in the following way: the line UCTRL# at the LSC, when low, indicates that the data lines UD[31..4] contain a user's private control code (e.g. end_of_block, block_address etc.). This causes the S-LINK to transmit this data in such a way that when the data is transferred from the LDC on lines LD[31..4], the line LCTRL# is set low for the duration of that word.

Note that when UCTRL# is set low, the data lines UD[3..0] and LD[3..0] are used by the S-LINK. That is, the data present on these lines at the LSC is ignored and the S-LINK itself generates the data which is transferred out of the LDC. Data lines UD[31..4] are transmitted and are transferred on LD[31..4] as normal. The reserved lines have the meanings detailed in Table 4. The reason for this scheme is to support the error detection function of the S-LINK which is described in Section 4.5.

For users who use the control/data bit to mark blocks of data, a data block is defined as the data words between two control words.

TABLE 4. Data Line Meanings When LCTRL# is Low
Same as UD[31..4]Reserved for future useReserved for future useWhen 1: Transmission error in Control Word.

When 0: Control Word OK

When 1: Transmission error in previous data block

When 0: Previous Data Block OK

The S-LINK Interface Specification - 27 MARCH 1997
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