H8SSLASH2218 datasheet(201/750 Pages) RENESAS

201 / 750 page

Section 6 Bus Controller

Rev.6.00 Jun. 03, 2008 Page 153 of 698

REJ09B0074-0600

6.9

Bus Release

The H8S/2218 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.

In external extended 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 this LSI. 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.

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 and external access request generation,

the order of priority is as follows:

(High) External bus release > Internal bus master external access (Low)

Table 6.5 shows pin states in the external bus released state.

In the H8S/2212 Group, the BRLE bit in BCRL should not be set to 1.

Table 6.5

Pin States in Bus Released State

Pins

Pin State

A23 to A0

High impedance

D15 to D0

High impedance

CSn

High impedance

HWR

High impedance

LWR

High impedance

H8S/2218 数据表(PDF) 201 Page - Renesas Technology Corp

H8S/2218 数据表(HTML) 201 Page - Renesas Technology Corp

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

数据表下载

链接网址

H8S/2218 数据表(PDF) 201 Page - Renesas Technology Corp

H8S/2218 数据表(HTML) 201 Page - Renesas Technology Corp

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

数据表 下载

链接网址

数据表下载