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CHAPTER 14 DTP/EXTERNAL INTERRUPT CIRCUIT
MB90560 series
14.5
14.5.2 DTP function
Operation of the DTP/External Interrupt Circuit
The DTP/external interrupt circuit has a DTP function that detects a signal supplied to a
DTP/external interrupt pin from an external peripheral and activates the extended
intelligent I/O service.
I
Operation of the DTP function
The DTP function detects a data transfer request signal from an external peripheral to
automatically transfer data between memory and the peripheral.
The extended intelligent I/O service (EI
2
OS) is activated by the external interrupt function using
level detection. The operation of the DTP function is the same as that of the external interrupt
function up to the point that the CPU accepts an interrupt request. If the operation of EI
2
OS is
enabled (ICR: ISE = 1), EI
2
OS is activated to start data transfer when an interrupt request is
accepted. When the transfer of one data unit ends, the descriptor is updated and the interrupt
request flag bit is cleared to wait for the next request from the pin. When the entire transfer using
EI
2
OS is completed, control is transferred to the interrupt processing routine.
The external peripheral signal must be removed only the level of the data transfer request signal
(DTP external interrupt cause) within three cycles of the first transfer.
Figure 14.5-3 Example of interfacing to the external peripheral
H-level request (ELVR: LB0, LA0 = 01
B
)
Input to the INT0 pin
(DTP external interrupt cause)
Internal operation of the
CPU (microprogram)
Address bus pin
Data bus pin
Descriptor selection
and reading
Descriptor updating
Read signal
Write signal
Read address
Read data
Write address
Write data
External
peripheral
(external
memory)
External
peripheral
Register
Data
transfer
request
Data, address bus
DTP external
interrupt cause (*2)
Internal data bus
Read operation(*1)
DTP/external
interrupt
circuit
Interrupt
request
Write operation (*3)
Internal
memory
*1, *2 Must be removed within three machine cycles of transfer.
*3 If the extended intelligent I/O service is in periphera
→
memory transfer mode.