Operation - NEC V850ES/SA2 UPD703201 Manual

12.3.4 Operation

(1) Transfer mode
CSIn transmits and receives data using three lines: 1 clock line and 2 data lines.
In reception-only mode (TRMDn = 0 in the CSIMn register), the transfer is started by reading the SIOn register.
To read the value of the SIOn register without starting reception, read the SIOEn register.
In transmission/reception mode (TRMDn = 1 in the CSIMn register), the transfer is started by writing data to
the SOTBn register.
When an 8-bit transfer of CSIn ends, the CSOTn bit of the CSIMn register becomes 0, and transfer stops
automatically. Also, when the transfer ends, a transmission/reception completion interrupt (INTCSIn) is
generated.
Cautions 1. When CSOTn bit = 1 in the CSIMn register, the control registers and data registers should
not be accessed.
2. If transmit data is written to the SOTBn register and the TRMDn bit of the CSIMn register
is changed from 0 to 1, serial transfer is not performed.
Remark n = 0 to 3 (V850ES/SA2)
n = 0 to 4 (V850ES/SA3)
(2) Serial clock
(a) When internal clock is selected as the serial clock
If reception or transmission is started, a serial clock is output from the SCKn pin, and the data of the SIn
pin is taken into the SIOn register sequentially or data is output to the SOn pin sequentially from the SIOn
register when the data is synchronized with the serial clock in accordance with the setting of the CKPn and
DAPn bits of the CSICn register.
(b) When external clock is selected as the serial clock
If reception or transmission is started, the data of the SIn pin is taken into the SIOn register sequentially or
output to the SOn pin sequentially in synchronization with the serial clock that has been input to the SCKn
pin following transmission/reception startup in accordance with the setting of the CKPn and DAPn bits of
the CSICn register.
If serial clock is input to the SCKn pin when neither reception nor transmission is started, a shift operation
will not be executed.
Remark n = 0 to 3 (V850ES/SA2)
n = 0 to 4 (V850ES/SA3)
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CHAPTER 12 SERIAL INTERFACE FUNCTION
Preliminary User's Manual U15905EJ1V0UD