Samsung S3C2500B User Manual page 419

S3C2500B IOM2 CONTROLLER
The monitor protocol is illustrated in figure9-2. Before the data in IOM2MTD register is transmitted, The IOM2
controller should verify that the transmission is idle, that is, MX/MR is inactive ("1") for two or more than 2
frames. When idle status is detected, the IOM2 controller forces the MX bit to go active ("0"), indicating the
presence of valid monitor data in the corresponding frame. As a result, the receiver stores the monitor data and
generates MRxBA(Monitor Rx Buffer Available) interrupt. When the IOM2MRD is read by the CPU in response to
the interrupt, the receiver forces MR bit to go active ("0"), indicating the acknowledge of received data.
In response to the acknowledge, the transmitter generates MTxBA(Monitor Tx Buffer Available) interrupt and the
CPU writes data to IOM2MTD. The MX bit is still in the active. The transmitter indicates a new byte in monitor
channel by returning the MX bit active after sending it once in the inactive state. When the MRxBA interrupt is
generated and the CPU read out the IOM2MRD, the receiver acknowledges the data by returning the MR bit
active after sending it once in the inactive state. This in turn causes the transmitter to generate an MTxBA
interrupt.
When the last byte has been transmitted and acknowledged, the CPU set the MTxEOM(End of Message
Request) to "1". This enforces inactive state in the MX bit. Two frames of MX inactive indicate the end of a
message. When the MX bit is received in the inactive state in two consecutive frames, the receiver generates the
MRxEOM(End of Message Received) interrupt and enforces an inactive state in the MR bit. This terminates the
Monitor channel transmission.
9.3.7.2 Transmission error
During the transmission process, the transmission is aborted only if errors in the MX/MR handshake protocol
occur. An abort is indicated by setting the MR bit inactive for two or more frames. The transmitter must react with
EOM. This situation is illustrated in the following figure9-3.
EOM
Transmitter MX
Receiver MR
Abort Request
Figure 9-3. Abortion of Monitor Channel Transmission
9-5