E62655RUSB Renesas Electronics America, E62655RUSB Datasheet - Page 240

• Manufacturer Part Number: E62655RUSB
• Description: EMULATOR BASE H8S/2655R W/USB
• Manufacturer: Renesas Electronics America
• Type: Microcontrollerr

Specifications of E62655RUSB

• Contents: E6000 Emulator Unit and 4 Logic Probes
• For Use With/related Products: H8S/2655R
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Section 6 Bus Controller
6.11
6.11.1
The H8S/2655 Group can release the external bus in response to a bus request from an external
device. In the external bus released state, the internal bus master continues to operate as long as
there is no external access.
If an internal bus master wants to make an external access in the external bus released state, or if a
refresh request is generated, it can issue a bus request off-chip.
6.11.2
In external expansion mode, the bus can be released to an external device by setting the BRLE bit
in BCRL to 1. Driving the BREQ pin low issues an external bus request to the H8S/2655 Group.
When the BREQ pin is sampled, at the prescribed timing the BACK pin is driven low, and the
address bus, data bus, and bus control signals are placed in the high-impedance state, establishing
the external bus-released state.
In the external bus released state, an internal bus master can perform accesses using the internal
bus. When an internal bus master wants to make an external access, it temporarily defers
activation of the bus cycle, and waits for the bus request from the external bus master to be
dropped. Even if a refresh request is generated in the external bus released state, refresh control is
deferred until the external bus master drops the bus request.
If the BREQOE bit in BCRL is set to 1, when an internal bus master wants to make an external
access in the external bus released state, or when a refresh request is generated, the BREQO pin is
driven low and a request can be made off-chip to drop the bus request.
When the BREQ pin is driven high, the BACK pin is driven high at the prescribed timing and the
external bus released state is terminated.
In the event of simultaneous external bus release request, refresh request, and external access
request generation, the order of priority is as follows:
Rev. 5.00 Sep 14, 2006 page 210 of 1060
REJ09B0331-05000
(High) Refresh > External bus release > Internal bus master external access (Low)
Bus Release
Overview
Operation