H8S2556 Datasheet, PDF (592/982 Pages) Renesas Technology Corp – 16-Bit Single-Chip Microcomputer H8S Family/H8S/2500 Series

Section 17 IEBus™ Controller (IEB) [H8S/2552 Group]
(When φ = 12, 18, or 24MHz)
Field name Header Master Slave address Control field Message
address field
field
length field
Data field
Number
of bits
Transfer
time
1 1 12 1
Start ^Broad- Master _P
bit ^cast address
bit
12
Slave
address
11
PA
4 11 8 11
Control
bits
P
A
Message
length
P
A
bits
8
Data
bits
11
PA
8 11
Data _{P A}
bits
Mode 0
Approximately 7330 μs
Approximately 1590 × N μs
Mode 1
Approximately 2090 μs
Approximately 410 × N μs
Mode 2
Approximately 1590 μs
Approximately 300 × N μs
P: Parity bit (1 bit)
A: Acknowledge bit (1 bit)
When A = 0: ACK
When A = 1: NAK
N: Number of bytes
Note: The value of acknowledge bit is ignored in broadcast communications.
Figure 17.2 Transfer Signal Format
(1) Header
Header is comprised of a start bit and a broadcast bit.
(a) Start Bit
The start bit is a signal for informing a start of data transfer to other units. A unit, which
attempts to start data transfer, outputs a low-level signal (start bit) for a specified period and
then outputs the broadcast bit.
If another unit is already outputting a start bit when a unit attempts to output a start bit, the unit
waits for completion of output of the start bit from the other unit without outputting the start
bit, and then outputs the broadcast bit synchronized with the completion timing.
Other units enter the receive state after detecting the start bit.
(b) Broadcast Bit
The broadcast bit is a bit to identify the type of communications: broadcast or normal.
When this bit is cleared to 0, it indicates the broadcast communications. When it is set to 1, it
indicates the normal communications. Broadcast communications includes group broadcast
and general broadcast, which are identified by a value of the slave address. (For details of the
slave address, see section 17.1.2 (3), Slave Address Field.)
Since there are multiple slave units, which are communications destination units, in the case of
broadcast communications, the acknowledge bit is not returned from each field described in (b)
and below.
Rev.5.00 Sep. 27, 2007 Page 546 of 932
REJ09B0099-0500