Hardware manual

Microcomputer Technical Q&A
76
Q&A No.: QAH8S-205
Category: DMAC
Subject: TEND Signal Output Conditions when Using Write Buffer
Function
Question
What are the TEND signal output conditions when the write buffer function is used?
Answer
The TEND output signal goes low in an external bus cycle if either a DMAC read cycle or write
cycle is an external access.
If a DMAC data transfer involves internal addresses, on the other hand, the TEND signal is not
output while the external bus is used (during external bus release, an external write using the write
buffer function, the DRAM refresh period, etc.). The TEND signal is output when the external bus
is not in use.
DMAC TEND signal output is shown in the table below.
DMAC TEND Signal Output
DMAC Access Area Read Write
External address → external address O O
Internal address → external address ∆ O
External address → internal address O O
Internal address → internal address ∆∆
Note: ∆ : Output when external bus is not being used
O : Always output