Datasheet

Section 14 IEBus™ Controller (IEB) [H8S/2258 Group]
Rev. 6.00 Mar. 18, 2010 Page 530 of 982
REJ09B0054-0600
The above registers can be specified in any order. (The register specification order does not affect
the IEB operation.)
(2) DTC Initialization
1. Set the start address of the RAM which stores the register information necessary for the DTC
transfer in the vector address (H'000004D2) to be accessed when a DTC transfer request is
generated.
2. Specify the following from the start address of the RAM.
⎯ Transfer source address (SAR): Address (H'FFF80D) of the IEBus receive buffer register
(IERBR).
⎯ Transfer destination address (DAR): Start address of the RAM which stores data received
from the data field.
⎯ Transfer count (CRA): Maximum number of transfer bytes in one frame in the transfer
mode.
3. Set DTCEG6 in the DTC enabler register G (DTCERG) to enable the RxRDY interrupt
(IETxI).
Because the above settings are performed before the frame reception, the length of data to be
received cannot be decided. Accordingly, the maximum number of transfer bytes in one frame is
specified as the DTC transfer count.
If the DTC is specified after reception starts, the above settings are performed in the receive start
(RxS) interrupt handling routine. In this case, the transfer count must be the same value as the
contents of the IEBus receive message length register (IERBFL).
(3) Slave Reception Flow
Figure 14.9 shows the slave reception flow. Numbers in the following description correspond to
the number in figure 14.9. In this example, the DTC is specified when the frame reception starts.
1. After the broadcast reception has been completed, the slave reception is performed. The
receive broadcast bit status flag (RSS) in IEFLG retains the previous frame information (set to
1) until the receive start detection flag (RxS) is set to 1. If the RSS flag changes at the timing
of header reception, the interrupt handling of the broadcast reception completion must be
completed before the header reception. Accordingly, the RSS flag is stipulated that it changes
at the timing of starting reception.
2. If data is received up to the message length field, a receive start detection (RxS) interrupt
(receive status interrupt (IERSI)) will occur and the SRE flag is set to 1. In this case, the DTC
initialization described in (2) is performed. After initialization, the RxS flag is cleared to 0.