NEC PD78F9488 - Manual (Page 249)

CHAPTER 12 SERIAL INTERFACE 1A0
User’s Manual U15331EJ4V1UD
249
(4) Timing of interrupt request signal generation
The interrupt request signal is generated in synchronization with the timing shown in Table 12-2.
Table 12-2. Timing of Interrupt Request Signal Generation
Operation Mode Timing of Interrupt Request Signal
Master mode 10th serial clock at end of transfer Single mode
Slave mode 8th serial clock at end of transfer
Repeat transmit mode Not generated
(5) Interval time of automatic transmission/reception
Because read/write to/from the buffer RAM using the automatic transmit/receive function is performed
asynchronously to the CPU processing, the interval time is dependent on the CPU processing of the timing of
the eighth rising of the serial clock and the set value of automatic data transmit/receive interval specification
register 0 (ADTI0). Whether the interval time is dependent on ADTI0 is selected by setting bit 7 (ADTI07) of
ADTI0. If ADTI07 is reset to 0, the interval time is 2/f
SCK
. If ADTI07 is set to 1, whichever is greater of the
interval time determined by the set contents of ADTI0 or the interval time (2/f
SCK
) determined by the CPU
processing is selected.
Figure 12-17 shows the interval time of automatic transmission/reception.
Remark f
SCK
: Serial clock frequency
Figure 12-17. Interval Time of Automatic Transmission/Reception
Interval
SCK10
D7 SO10
SI10
CSIIF10
D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D2 D1 D0
The following expression must be satisfied to access the buffer RAM.
1 transfer cycle + Interval time
≥ Read access + Write access + CPU buffer RAM access (time)
In the case of a “high-speed CPU & low-speed SCK”, the interval time is not necessary. In the case of a
“low-speed CPU & high-speed SCK”, the interval time is necessary.
In this case, make sure that a sufficient interval time elapses, by using automatic data transmit/receive
interval specification register 0 (ADTI0), so that the above expression is satisfied.