CN8478/CN8474A/CN8472A/CN8471A
7.0 Electrical and Mechanical Specifications
Multichannel Synchronous Communications Controller (MUSYCC™)
7.2 Timing and Switching Specifications
Figure 7-14. EBUS Write/Read Transactions, Motorola-Style
See Notes
ECLK
1
2
3
4
5
6
7
8
9
10
BR*
BG*
BGACK*
EAD[31:0]
EBE[3:0]*
Address
Data
Byte Enables from PCI Data Phase
AS*
R/WR* (read)
R/WR* (write)
DS*
ALAPSE = 0
ELAPSE = 0
BLAPSE = 0
8478_036
NOTE(S):
1. BG* assertion depends on the external bus arbiter. While BG* and BR* are both deasserted, MUSYCC places shared
EBUS signals in high impedance (three-state, as shown by dashed lines).
2. One ECLK cycle after BG* assertion, MUSYCC outputs valid command bus signals: EBE, AS*, R/WR*, and DS*.
3. Two ECLK cycles after BG* assertion, MUSYCC outputs valid EAD address signals. BGACK* assertion occurs three ECLK
cycles after BG* and BR* are both asserted.
4. ALAPSE inserts a variable number of ECLK cycles to extend AS* high pulse width and EAD address interval.
5. EAD address remains valid for one ECLK cycle after AS* falling edge. During a write transaction, MUSYCC asserts R/WR*
and outputs valid EAD write data one ECLK prior to DS* assertion. During a read transaction, EAD data lines are input.
6. ELAPSE inserts a variable number of ECLK cycles to extend DS* low pulse width and EAD data interval. Read data inputs
are sampled on ECLK rising edge coincident with DS* deassertion.
7. EAD write data, EBE, R/WR*, and AS* signals remain valid for one ECLK cycle after BGACK* and DS* are deasserted.
8. One ECLK cycle after BGACK* deassertion, the BR* output is deasserted and the bus is parked (command bus deasserted,
EAD three-state). The bus parked state ends when the external bus arbiter deasserts BG*.
9. Command bus is unparked (three-stated) one ECLK after BG* deassertion; two different unpark phases are shown,
indicating the dependence on BG* deassertion. If BG* remained asserted until the next bus request, then command bus
remains parked until one ECLK following the next BR* assertion. Warning: Whenever BG* is deasserted, all shared EBUS
signals are forced to three-state after one ECLK cycle, regardless of whether the EBUS transaction was completed.
MUSYCC will not reissue or repeat such an aborted transaction.
10. BLAPSE inserts a variable number of ECLK cycles to extend BR* deassertion interval until the next bus request.
100660E
Conexant
7-15
CONEXANT [ CONEXANT SYSTEMS, INC ]
