Automatic Transmission Mode Operation Timing - NEC 78K0 User Manual

(b) Automatic transmission mode
In this mode, the specified number of 8-bit unit data is transmitted.
Serial communication is started when bit 0 (ATSTA0) of serial trigger register 0 (CSIT0) is set to 1 while
bit 7 (CSIAE0), bit 6 (ATE0), and bit 3 (TXEA0) of serial operation mode specification register 0
(CSIMA0) are set to 1.
When the final byte has been transmitted, an interrupt request flag (ACSIIF) is set. The termination of
automatic transmission and reception can also be judged by bit 0 (TSF0) of serial status register 0
(CSIS0).
If a receive operation, busy control and strobe control are not executed, the SIA0/P143,
BUSY0/BUZ/INTP7/P141, and STB0/P145 pins can be used as normal I/O port pins.
Figure 17-16 shows the automatic transmission mode operation timing, and Figure 17-17 shows the
operation flowchart. Figure 17-18 shows the operation of the internal buffer RAM when 6 bytes of data
are transmitted.
Figure 17-16. Automatic Transmission Mode Operation Timing
SCKA0
SOA0 D7 D6 D5 D4 D3 D2 D1 D0
ACSIIF
TSF0
Cautions 1. Because, in the automatic transmission mode, the automatic transmit/receive
function reads data from the internal buffer RAM after 1-byte transmission, an
interval is inserted until the next transmission. As the buffer RAM read is performed
at the same time as CPU processing, the interval is dependent upon the value of
automatic data transfer interval specification register 0 (ADTI0) and the set values of
bits 5 and 4 (STBE0, BUSYE0) of serial status register 0 (CSIS0) (see (5) Automatic
transmit/receive interval time).
2. If an access to the buffer RAM by the CPU conflicts with an access to the buffer
RAM by serial interface CSIA0 during the interval period, the interval time specified
by automatic data transfer interval specification register 0 (ADTI0) may be extended.
Remark ACSIIF: Interrupt request flag
TSF0:
CHAPTER 17 SERIAL INTERFACE CSIA0
Interval
*
Bit 0 of serial status register 0 (CSIS0)
User's Manual U15947EJ2V0UD
D7 D6 D5 D4 D3 D2 D1 D0
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