Fujitsu MCM3130SS Manuale Utente

C156-E228-02EN 7-15 

Table 7.7 gives the timing required for operations on the SCSI bus. 

Table 7.7 lists SCSI FAST-20 timing specifications for operations on the SCSI 
bus.  Table 7.8 lists asynchronous, SCSI-1, and FAST-SCSI timing specifications. 

No. Name 

Standard 

Timing 

specification 

1 

Arbitration Delay 

2.4 µs min. 

The minimum wait period between the time the SCSI 
device sends a BSY signal and the time the value on the 
data bus for determining the priority of bus use is judged 
in the ARBITRATION phase.  A maximum time is not 
defined. 

2 

Assertion Period 

15 ns min. 

Minimum pulse width of an ACK signal sent by INIT 
and an REQ signal sent by TARG for synchronous data 
transfer. 

3 

Bus Clear Delay 

800 ns max. 

Maximum allowable period between the time either of 
the following events occurs and the time the SCSI 
device stops driving all bus signals. 

(1)  Detection of the BUS FREE phase (when both 

BSY and SEL signal become false during Bus 
Settle Delay). 

Maximum allowable period between the time both 
BSY and SEL signal became false and the time the 
bus is released is 1,200 ns.  

An SCSI device that requires a period longer than 
Bus Settle Delay for the detection of the BUS 
FREE phase must release the bus within (Bus 
Clear Delay) minus (Bus Settle Delay excess time). 

(2)  Another SCSI device asserts the SEL signal during 

an ARBITRATION phase. 

(3)  The RST signal becomes true (RESET condition). 

4 

Bus Free Delay 

800 ns min. 

Minimum wait period between the time the SCSI device 
detects a BUS FREE phase and the time it sends a BSY 
signal to initiate an ARBITRATION phase. 

5 

Bus Set Delay 

1.8 µs max. 

Maximum allowable period between the time an SCSI 
device detects a BUS FREE phase and the time it sends 
BSY and SCSI ID signals to initiate an ARBITRATION 
phase.