Specifications

Serial Communications (V40)
PROGRAMMABLE REGISTERS
Six registers are used for communication with the SCU. The Serial
Transmit Buffer (STB) and Serial Receive Buffer (SRB) store data to
be transferred to the serial link and from the serial link, respectively.
The Serial Command (SCM) and Serial Mode (SMD) registers define
the operating mode. The Serial Interrupt Mask (SIMK) register
controls the receive and transmit interrupts. The Serial Status (SST)
register provides information on the current state of the transmitter
and receiver.
The base I/O address of the SCU registers is defined by the OPHA
and SULA registers. OPHA is programmed with the high byte and
SULA with the low byte of the 16-bit address; see page 6-5 for
details. The address of each register, relative to the base address, is
shown in Table 10-1.
Table 10-1
SCU Register Addressing.
Page
Address Register Operation Number
Base + 0 Receive Buffer Read 10-5
Base + 0 Transmit Buffer Write 10-5
Base + 1 Status Register Read 10-6
Base + 1 Command Register Write 10-8
Base + 2 Mode Register Write 10-9
Base + 3 Interrupt Mask Register Read/Write 10-10
10-5