Rockwell RFX144V24-S23, Руководство дизайнера

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RFX144V24-S23 and RFX96V24-S23 Modem Designer’s Guide
1070 2-7
Table 2-3. MDP Hardware Interface Signal Definitions (Cont’d)
Label I/O Type Signal/Definition
~READ–ø2 IA Read Enable–ø2. When ~EN85 is low (8085 bus selected), reading is controlled by the host pulsing ~READ
input low during the microprocessor bus access cycle. The read timing is:
Parameter Symbol Min. Max. Units
~CS Setup Time TCS 0 – ns
RSi Setup Time TRS 10 – ns
Data Access Time TDA – 45 ns
Data Hold Time TDHR 10 – ns
Control Hold Time THC 10 – ns
Phase 2 (ø2) Clock High TP2CH 70 – ns
Notes:
1. ~CS and ~READ must not both be active continuously.
2. A read or write operation following a read operation must be delayed by at least 1 YCLK cycle.
~WRITE–R/~W IA Write Enable–R/~W. When ~EN85 is low (8085 bus selected), writing is controlled by the host pulsing ~WRITE
input low during the microprocessor bus access cycle. The write timing is:
Parameter Symbol Min. Max. Units
~CS Setup Time TCS 0 – ns
RSi Setup Time TRS 10 – ns
Control Hold Time THC 10 – ns
Write Data Setup Time TWDS 20 – ns
Write Data Hold Time TDHW 10 – ns
Phase 2 (ø2) Clock High TP2CH 70 – ns
Notes:
1. A read or write operation following a write operation must be delayed by at least 2 YCLK cycles.
~IRQ1,
~IRQ2
OC,
OC
Interrupt Request. ~IRQ1 and ~IRQ2 interrupt request outputs may be connected to the host processor
interrupt request input in order to interrupt host program execution for immediate modem service. (The term,
“~IRQ,” refers to both the ~IRQ1 and ~IRQ2 output lines in the following discussion.) The ~IRQ output can be
enabled in DSP interface memory to indicate immediate change of conditions in the modem. The use of ~IRQ is
optional depending upon modem application.
The ~IRQ output structure is an open-drain field-effect-transistor (FET). The ~IRQ output can be wire-ORed
with other ~IRQ lines in the application system. Any of these sources can drive the host interrupt input low, and
the host interrupt servicing process normally continues until all interrupt requests have been serviced (i.e., all
~IRQ lines have returned high).
Because of the open-drain structure of ~IRQ, an external pull-up resistor to +5V is required at some point on the
~IRQ line. The resistor value should be small enough to pull the ~IRQ line high when all ~IRQ drivers are off
(i.e., it must overcome the leakage currents). The resistor value should be large enough to limit the driver sink
current to a level acceptable to each driver. If only the modem ~IRQ output is used, a resistor value of 5.6K
ohms, 20%, 0.25 W, is sufficient.