LSI LSI53C1000, Technical Manual

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SCSI Functional Description 2-43
Bit 2, XCLKH_ST (Extra Clock of Data Hold on ST transfer edge), adds
a clock of data hold to synchronous DT or ST SCSI transfers on the ST
edge. This bit impacts DT and ST transfers as it affects data hold to the
ST edge. Setting this bit reduces the synchronous transfer send rate but
does not reduce the rate at which the LSI53C1000 receives outbound
REQs, ACKs, or data.
Bit 1, XCLKS_DT (Extra Clock of Data Setup on DT transfer edge), adds
a clock of data setup to synchronous DT SCSI transfers on the DT edge.
This bit only impacts DT transfers as it only affects data hold to the DT
edge. Setting this bit reduces the synchronous transfer send rate but
does not reduce the rate at which the LSI53C1000 receives outbound
REQs, ACKs, or data.
Bit 0, XCLKS_ST (Extra Clock of Data Setup on ST transfer edge), adds
a clock of data setup to synchronous DT or ST SCSI transfers on the ST
edge. This bit impacts DT and ST transfers as it affects data hold to the
ST edge. Setting this bit reduces the synchronous transfer send rate but
does not reduce the rate at which the LSI53C1000 receives outbound
REQs, ACKs, or data.
2.2.15.3 Determining the Data Transfer Rate
The synchronous receive rate can be calculated using the following
formula:
Note : The receive rate is independent of the settings of the
XCLKS_DT, XCLKS_ST, XCLKH_DT, XCLKH_ST bits.
The synchronous send rate, in units of megatransfers/s, can be
calculated using the following formula:
Receive Rate (DT)
Input Clock Rate
SCF Divisor 2
× ( )
---------------------------------------------- (Megatransfers/s) =
Receive Rate (ST)
Input Clock Rate
SCF Divisor 4
× ( )
---------------------------------------------- (Megatransfers/s) =
Send Rate (DT)
Input Clock Rate
SCF Divisor 2
XXXXCLKH_ST
2
-------------------------------------------------------------------------------------------------------------------------------------- +
 
 
×
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- =
Send Rate (ST)
Input Clock Rate
SCF Divisor 4 XXCLKH_ST
+
( ) ×
---------------------------------------------------------------------------------------------------------------------- =