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CHAPTER 17 DTP/EXTERNAL INTERRUPTS
17.4.2 DTP Function
The DTP/external interrupt has the DTP function that detects the signal of the external
peripheral device from the DTP/external interrupt pin to start the EI
2
OS.
■ DTP Function
The DTP function detects the signal level set by the detection level setting register of the DTP/external
interrupt function to start the EI
2
OS.
• When the EI
2
OS operation is already enabled (ICR:ISE = 1) at the point when the interrupt request is
accepted by the CPU, the DTP function starts the EI
2
OS and starts data transfer.
• When transfer of one data item is completed, the descriptor is updated and the DTP/external interrupt
request flag bit is cleared to prepare for the next request from the DTP/external interrupt pin.
• When the EI
2
OS completes transfer of all the data, control branches to the interrupt processing.
Figure 17.4-3 Example of Interface with External Peripheral Device (when using EI
2
OS in Single-chip
mode)
CPU
(EI
2
OS)
DTP factor *
1
INT
*1: This must be cancelled within three machine clocks after the start of data transfer.
*2: When EI
2
OS is "peripheral function" "internal memory transfer".
Descriptor
renewal
Descriptor
select and read
High level request (ELVR1: LB8, LA8=01
B)
Input to INT8 pin
(DTP factor)
CPU internal operation
Internal data bus
Read and
write operation*
2
Internal
memory
Interrupt
request
DTP/external
interrupt
circuit
Data transfer
request
Peripheral
device
of external
connection