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16.5.2 DTP Function
The DTP/external interrupt circuit has the DTP function that detects the signal of the external peripheral unit
via the DTP/external interrupt pin to start the EI
n Operation of DTP function
The DTP function detects the data transfer request signal sent from the external peripheral unit and transfers
data automatically between memory and the resource. The level detection external interrupt function starts
2
the EI
OS. The DTP function performs the same operation as the external interrupt function until the
interrupt request is accepted by the CPU. When the EI
the point when the interrupt request is accepted by the CPU, the DTP function starts the EI
data transfer. When transfer of one data item is completed, updating the descriptor is performed and the
interrupt request flag bit is cleared to prepare for the next request from the pin. When the EI
transfer of all the data, control branches to the interrupt-processing routine. The external peripheral unit
must cancel only the level of the data transfer request signal (DTP factor) within three machine clocks after
the start of the first data transfer.
Input to INT0 pin
(DTP Factor)
Internal operation of CPU
(microprogram)
Address bus pin
Data bus pin
Read signal
Write signal
Peripheral
unit external-
connected
Register
DTP factor
Data transfer
request
*1, *2 : This must be cancelled within three machine clocks after the start of data transfer.
2
*3
: When EI
DTP/EXTERNAL INTERRUPT CIRCUIT
H level request (ELVR: LB0, LA0 = 01
Descriptor
select/read
Read operation
*2
INT
DTP/External
interrupt
OS transfers data from resource to memory
Fig. 16.9 Example of Interface with External Peripheral Unit
2
OS.
2
OS operation is already enabled (ICR: ISE = 1) at
Read address
Internal data bus
*1
Interrupt
request
CPU
(EI
circuit
16-15
)
B
Descriptor
Write address
Read data
Write data
*1
*3
Write operation
Internal
2
OS)
memory
2
OS and starts
2
OS completes
update
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