7.0 Electrical and Mechanical Specifications
CN8478/CN8474A/CN8472A/CN8471A
7.2 Timing and Switching Specifications
Multichannel Synchronous Communications Controller (MUSYCC™)
7.2.4 EBUS Arbitration Timing
Illustrated in Figures 7-13 and 7-14 are Intel- and Motorola-style write and read
transactions.
Figure 7-13. EBUS Write/Read Transactions, Intel-Style
1
2
3
4
5
6
7
8
9
10
See Notes
ECLK
HOLD
HLDA
Address
Data
EAD[31:0]
EBE[3:0]*
ALE
Byte Enables from PCI Data Phase
RD* (write)
WR* (write)
RD* (read)
WR* (read)
ALAPSE = 0
ELAPSE = 0
BLAPSE = 0
8478_035
NOTE(S):
1. HLDA assertion depends on the external bus arbiter. While HOLD and HLDA are both deasserted, MUSYCC places shared
EBUS signals in high impedance (three-state, shown as dashed lines).
2. MUSYCC outputs valid command bus signals: EBE, ALE, RD*, and WR* 1 ECLK cycle after HLDA assertion.
3. MUSYCC outputs valid EAD address signals, 2 ECLK cycles after HLDA assertion.
4. ALE assertion occurs 3 ECLK cycles after HOLD and HLDA are both asserted.ALAPSE inserts a variable number of ECLK
cycles to extend ALE high pulse width and EAD address interval.
5. EAD address remains valid for 1 ECLK cycle after ALE falling edge. During a write transaction, MUSYCC outputs valid EAD
write data 1 ECLK prior to WR* assertion. During a read transaction, EAD data lines are inputs.
6. ELAPSE inserts a variable number of ECLK cycles to extend RD*/WR* low pulse width and EAD data intervals. Read data
inputs are sampled on ECLK rising edge coincident with RD* deassertion.
7. EAD write data and EBE byte enables remain valid for 1 ECLK cycle after RD*/WR* deassertion.
8. HOLD is deasserted, and the bus is parked (command bus deasserted, EAD tristate) 1 ECLK after RD* or WR* deassertion.
The bus parked state ends when HLDA is deasserted, 1 ECLK after RD* or WR* deassertion.
9. Command bus is unparked (three-stated) one ECLK after HLDA deassertion; two different unpark phases are shown,
indicating the dependence on HLDA deassertion. If HLDA remained asserted until the next bus request, then command bus
remains parked until 1 ECLK cycle following the next HOLD assertion. Warning: Whenever HLDA is deasserted, all shared
EBUS signals are forced to three-state after 1 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 HOLD deassertion interval until the next bus request.
7-14
Conexant
100660E
CONEXANT [ CONEXANT SYSTEMS, INC ]
