R01UH0822EJ0100 Rev.1.00
Page 236 of 1041
Jul 31, 2019
RX13T Group
15. Buses
15.2.5
Write Buffer Function (Internal Peripheral Bus)
The internal peripheral bus has the write buffer function, which allows the next round of bus access to start, before the
current write access is completed, in write access. However, if the following round of bus access is from the same bus
master but to the different internal peripheral bus, it is suspended until the bus operations already in progress are
completed. When read access to the internal memory is scheduled after the write access to the internal peripheral bus
from the CPU, the following round of bus access can be started before the current bus operation is completed and thus
the order of accesses may be changed (see
Figure 15.3
Write Buffer Function
Internal peripheral bus 2
Internal peripheral bus 1
Memory bus 1
RAM
RAM
Write access to peripheral bus 1
Access by the CPU:
(1) Peripheral bus 1 (W)
(2) Peripheral bus 1 (W)
(3) Peripheral bus 2 (W)
(4) Peripheral bus 2 (W)
(5) RAM (R)
(6) RAM (R)
Number of access cycles: 1 cycle (peripheral bus 1), 2 cycles (peripheral bus 2)
(1)
(2)
(5)
(6)
(3)
(4)
Write access to peripheral bus 2
Read access to RAM
Peripheral bus 2
Peripheral bus 2
Peripheral
bus 1
Peripheral
bus 1