14 SYNCHRONOUS SERIAL INTERFACE (SPIA)
S1C31D50/D51 TECHNICAL MANUAL
Seiko Epson Corporation
14-13
(Rev. 2.00)
14.7 DMA Transfer Requests
The SPIA has a function to generate DMA transfer requests from the causes shown in Table 14.7.1.
Table 14.7.1 DMA Transfer Request Causes of SPIA
Cause to request
DMA transfer
DMA transfer request flag
Set condition
Clear condition
Receive buffer
full
Receive buffer full flag
(SPIA_nINTF.RBFIF)
When data of the specified bit length is received and the
received data is transferred from the shift register to the
received data buffer
Reading the
SPIA_nRXD
register
Transmit buffer
empty
Transmit buffer empty flag
(SPIA_nINTF.TBEIF)
When transmit data written to the transmit data buffer is
transferred to the shift register
Writing to the
SPIA_nTXD
register
The SPIA provides DMA transfer request enable bits corresponding to each DMA transfer request flag shown
above for the number of DMA channels. A DMA transfer request is sent to the pertinent channel of the DMA con-
troller only when the DMA transfer request flag, of which DMA transfer has been enabled by the DMA transfer
request enable bit, is set. The DMA transfer request flag also serves as an interrupt flag, therefore, both the DMA
transfer request and the interrupt cannot be enabled at the same time. After a DMA transfer has completed, disable
the DMA transfer to prevent unintended DMA transfer requests from being issued. For more information on the
DMA control, refer to the “DMA Controller” chapter.
14.8 Control Registers
SPIA Ch.
n
Mode Register
Register name
Bit
Bit name
Initial
Reset
R/W
Remarks
SPIA_nMOD
15–12 –
0x0
–
R
–
11–8 CHLN[3:0]
0x7
H0
R/W
7–6 –
0x0
–
R
5
PUEN
0
H0
R/W
4
NOCLKDIV
0
H0
R/W
3
LSBFST
0
H0
R/W
2
CPHA
0
H0
R/W
1
CPOL
0
H0
R/W
0
MST
0
H0
R/W
Bits 15–12 Reserved
Bits 11–8 CHLN[3:0]
These bits set the bit length of transfer data.
Table 14.8.1 Data Bit Length Settings
SPIA_nMOD.CHLN[3:0] bits
Data bit length
0xf
16 bits
0xe
15 bits
0xd
14 bits
0xc
13 bits
0xb
12 bits
0xa
11 bits
0x9
10 bits
0x8
9 bits
0x7
8 bits
0x6
7 bits
0x5
6 bits
0x4
5 bits
0x3
4 bits
0x2
3 bits
0x1
2 bits
0x0
Setting prohibited