
III PERIPHERAL BLOCK: SERIAL INTERFACE
B-III-8-24
EPSON
S1C33L01 FUNCTION PART
The interrupt priority register sets the interrupt priority level of each interrupt source in a range between 0 and 7.
An interrupt request to the CPU is accepted only when no other interrupt request of a higher priority has been
generated.
In addition, only when the PSR's IE bit = "1" (interrupts enabled) and the set value of the IL is smaller than the
input interrupt level set by the interrupt priority register, will the input interrupt request actually be accepted by
the CPU.
For details on these interrupt control registers, as well as the device operation when an interrupt has occurred,
refer to "ITC (Interrupt Controller)".
Intelligent DMA
The receive-buffer full interrupt and transmit-buffer empty interrupt factors can be used to invoke intelligent
DMA (IDMA). This enables successive transmit/receive operations between memory and the
transmit/receive-buffer to be performed by means of a DAM transfer.
The following shows the IDMA channel numbers set for each interrupt factor:
IDMA Ch.
Ch.0 receive-buffer full interrupt:
0x17
Ch.0 transmit-buffer empty interrupt: 0x18
Ch.1 receive-buffer full interrupt:
0x19
Ch.1 transmit-buffer empty interrupt: 0x1A
The IDMA request and enable bits shown in Table 8.8 must be set to "1" for IDMA to be invoked. Transfer
conditions, etc. on the IDMA side must also be set in advance.
Table 8.8
Control Bits for IDMA Transfer
Channel
Interrupt factor
IDMA request bit
IDMA enable bit
Ch.0
Receive-buffer full
RSRX0(D6/0x40292)
DESRX0(D6/0x40296)
Transmit-buffer empty
RSTX0(D7/0x40292)
DESTX0(D7/0x40296)
Ch.1
Receive-buffer full
RSRX1(D0/0x40293)
DESRX1(D0/0x40297)
Transmit-buffer empty
RSTX1(D1/0x40293)
DESTX1(D1/0x40297)
If an interrupt factor occurs when the IDMA request and enable bits are set to "1", IDMA is invoked. No
interrupt request is generated at that point. An interrupt request is generated upon completion of the DMA
transfer. The bits can also be set so as not to generate an interrupt, with only a DAM transfer performed.
For details on DMA transfer and how to control interrupts upon completion of DMA transfer, refer to "IDMA
(Intelligent DMA)".
High-speed DMA
The receive-buffer full interrupt and transmit-buffer empty interrupt factors can also invoke high-speed DMA
(HSDMA).
The following shows the HSDMA channel number and trigger set-up bit corresponding to each channel:
Table 8.9
HSDMA Trigger Set-up Bits
SIF
Ch.
HSDMA Ch.
Trigger set-up bits
0
HSD0S[3:0] (D[3:0]) / HSDMA Ch.0/1 trigger set-up register (0x40298)
1
HSD1S[3:0] (D[7:4]) / HSDMA Ch.0/1 trigger set-up register (0x40298)
0
2
HSD2S[3:0] (D[3:0]) / HSDMA Ch.2/3 trigger set-up register (0x40299)
1
3
HSD3S[3:0] (D[7:4]) / HSDMA Ch.2/3 trigger set-up register (0x40299)
For HSDMA to be invoked by the receive-buffer full interrupt factor, the trigger set-up bits should be set to
"1010". For HSDMA to be invoked by the transmit-buffer empty interrupt factor, the trigger set-up bits should
be set to "1011". Transfer conditions, etc. must also be set on the HSDMA side.
The HSDMA channel is invoked through generation of the interrupt factor.
For details on HSDMA transfer, refer to "HSDMA (High-Speed DMA)".