Fujitsu MBA3147RC, MBC2036RC, MBC2073RC, MBA3300RC, MBA3073RC specifications Data information unit

1.6 Transport layer

1.6.2.4DATA information unit

Table 1.40 defines the data IU. The DATA frame is sent by an SSP INIT port to deliver write data (i.e., a write DATA frame) and is sent by an SSP TARG port to deliver read data (i.e., a read DATA frame). The maximum size of the data IU is the maximum size of any IU in an SSP frame. The minimum size of the data IU is one byte.

Table 1.40 DATA information unit

Bit	7	6	5		4	3	2	1	0
Byte
0				DATA (1byte to 1024bytes)
n-1

An SSP INIT port shall only transmit a write DATA frame:

a)in response to an XFER_RDY frame; or

b)after transmitting a COMMAND frame if the ENABLE FIRST BURST field in the COMMAND frame was set to one and the FIRST BURST SIZE field in the Disconnect-Reconnect mode page is not zero.

However, since drives do not support the FIRST BURST SIZE field, a drive can receive data only when it requests data with XFER_RDY frames.

If the value in the MAXIMUM BURST SIZE field on the Disconnect-Reconnect mode page is not zero, the maximum amount of data that is transferred at one time by an SSP TARG port per I_T_L_Q nexus is limited by the value in the MAXIMUM BURST SIZE field.

Drives do not support the MAXIMUM BURST SIZE field. However, the maximum data amount a drive can request with a single XFER_RDY frame is limited to 64 Kbytes.

An SSP TARG port shall set the NUMBER OF FILL BYTES field to zero in the frame header in all read DATA frames for a command except the last read DATA frame for that command. The SSP TARG port may set the NUMBER OF FILL BYTES field to a non-zero value in the last read DATA frame for a command (i.e., only the last read DATA frame for a command may contain data with a length that is not a multiple of four).

An SSP INIT port may set the NUMBER OF FILL BYTES field to a non-zero value contained in the last DATA frame that is sent as a response to an XFER_RDY frame. In this case, the SSP INIT port must set zeros in the NUMBER OF FILL BYTES fields in the frame headers of all the other data frames to be sent.

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