UPD784915B Datasheet, PDF (52/86 Pages) NEC – 16-BIT SINGLE-CHIP MICROCONTROLLERS

µPD784915B, 784916B
4.1.3 Macro service
The macro service is a function to transfer data between the memory and a special function register (SFR) without
intervention by the CPU. A macro service controller accesses the memory and SFR and directly transfers the data.
Because the status of the CPU is not saved or restored, data can be transferred more quickly than context switching.
The processing that can be executed with the macro service is described below.
Figure 4-3. Macro Service
CPU
Memory
Read Macro service Write
Write
controller
Read
SFR
Internal bus
(1) Counter mode
In this mode, the value of the macro service counter (MSC) is decremented when an interrupt request occurs.
This mode can be used to execute the division operation of an interrupt or count the number of times an interrupt
has occurred.
When the value of the macro service counter has been decremented to 0, a vector interrupt occurs.
MSC
-1
(2) Compound data transfer mode
When an interrupt request occurs, data are simultaneously transferred from an 8-bit SFR to memory, a 16-bit
SFR to memory (word), memory (byte) to an 8-bit SFR, and memory (word) to a 16-bit SFR (3 points MAX. for
each transfer).
This mode can also be used to exchange data, instead of transferring data.
This mode can be used for automatic transfer/reception by the serial interface or automatic updating of data/timing
by the serial output port.
When the value of the macro service counter reaches to 0, a vector interrupt request occurs.
Memory
SFR<4>-1 SFR<4>-2 SFR<4>-3
SFR<3>-1
SFR<3>-2
SFR<3>-3
...
Internal bus
SFR<2>-1 SFR<2>-2 SFR<2>-3
SFR<1>-1
SFR<1>-2
SFR<1>-3
Internal bus
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