VP2611 Просмотр технического описания (PDF) - Mitel Networks
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VP2611 Datasheet PDF : 14 Pages
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VP2611
CBUS Control Port
The CBUS control port is used to input control and setup
information and also to output status information. In order to
save on pin count, a microprocessor driving this port is
required to execute two I/O instructions in order to transfer a
single byte of information to or from the device. The first
transfer is always a write operation, with a low level on the
single address line which is used by the interface. Data on the
bus then defines the instructions listed in Table 3. The second
transfer can be a read or write operation as necessary, but the
address line must then be high with the set up time given in
Figure 10.
In addition to the single addresss line (CADR), data
transfers use a control strobe (CSTR) which is only effective
when a chip enable is present (CEN). Detailed timing informa-
tion is given in Figure 10, and when writing data or instructions
to the VP2615 the set up and hold times which are referenced
to the rising edge of CSTR must be maintained.
When a write instruction has been defined CADR should
be pulled high, valid data presented to CBUS7:0 and then
strobed in using CSTR. Other system I/O transfers can occur
between defining a write operation and supplying the data to
be written, assuming CEN is not active during those other
transfers. If CSTR does not go active because of I/O transfers
to other devices, then CEN can remain active low between the
instruction and data.
When a read instruction has been specified the requested
data will then be output on CBUS7:0 after the access time
specified from CEN going low, assuming that CADR was
already high. Otherwise the data will become valid after the
access time specified from CADR going high after CEN was
G
O O C US
WRITING DATA FROM THE CBUS:
This diagram shows a typical instruction and associated data field being written to the device.
CEN
10ns
20ns
10ns
CADR
CSTR
CBUS
I/P
20ns
20ns
10ns
20ns
20ns
10ns
INSTRUCTION
20ns
20ns
10ns
20ns
20ns
10ns
DATA IN
READING INFORMATION ON CBUS :
This diagram shows a typical instruction and associated data field being read from the device.
CEN
CADR
CSTR
CBUS
20ns
20ns
10ns
Th
10ns
20ns
20ns
10ns
INSTRUCTION
20ns
50ns
10ns
10ns
20ns
20ns
20ns*
20ns*
10ns
20ns*
DATA OUT
If Th is less than 5 ns then CBUS may be driven by the VP2615until CEN going high eventually turns off
the drivers. It will not prevent correct data being read when CEN again goes active
N.B. All timings shown are minimum values except those marked * which are maximums.
Fig 10 : Use of the Control Port
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