
CHAPTER 12 NBD FUNCTION (
μ
PD70F3116)
637
User’s Manual U14492EJ5V0UD
12.6 Restrictions on NBD
12.6.1 General restrictions
(1) CLK_DBG operates at less than half the speed of the internal system clock (f
XX
) and is 12.5 MHz maximum.
(2) If a command packet is sent during a reset period, “ready” is not returned afterwards. Reset again.
12.6.2 Restrictions related to read or write of RAM by NBD
(1) Initialize the DMA controller in user software.
(2) On a write, RAM can only be accessed in 32-bit units.
On a read-only, RAM can be accessed in 32-, 16-, or 8-bit units.
On a read/write, RAM can be accessed in 32-bit units.
(3) NBD does not function from the start of reset until completion of DMA controller initialization after the reset.
If a read or write of RAM is performed in this interval, NBD does not return “ready” afterwards. Reset again.
12.6.3 Restrictions related to NBD event trigger function
(1) If a ROM execution address event trigger is set to the address after a branch instruction, an event is
generated due to pipeline processing even if it is not executed. The trigger must be set to an address at least
32 bits
×
3 words after a branch instruction.
(2) Since an event trigger is cleared by a reset, it must be set again after a reset.
(3) Unless there is a ROM fetch, a trigger occurs even on a read.
(4) ROM address match functions only for internal ROM. The lower 2 bits are masked.
RAM address match functions only for internal RAM. The lower 2 bits are masked.
Caution ROM and RAM address match cannot be used in the in-circuit emulator.
12.6.4 How to detect termination of DMA initialization via NBD tool
Set an event trigger using a RAM write and send a write command from NBD to the relevant address. If an event
trigger occurs at this time, DMA initialization has terminated.