Serial Management Controllers (SMCs)
MOTOROLA
MC68360 USER’S MANUAL
7-271
descriptions. The part of the SMC parameter RAM that is the same for the UART and trans-
parent SMC protocols is shown in Table 7-12. The following discussion does not apply to
the GCI SMC protocol, which has its own parameter RAM.
NOT E: The boldfaced items should be initialized by the user.
Certain parameter RAM values (marked in boldface) need to be initialized by the user before
the SMC is enabled; other values are initialized/written by the CP. Once initialized, most
parameter RAM values will not need to be accessed in user software since most of the activ-
ity is centered around the transmit and receive BDs, not the parameter RAM. However, if
the parameter RAM is accessed by the user, the following restrictions should be noted. The
parameter RAM can be read at any time. The parameter RAMvalues related to the SMC
transmitter can only be written whenever the TEN bit in the SMC mode register is zero, after
a STOP TRANSMIT and before a RESTART TRANSMIT command. The parameter RAM
values related to the SMC receiver can only be written whenever the REN bit in the SMC
mode register is zero or if the receiver has previously been enabled after an ENTER HUNT
MODE command or CLOSE Rx BD command before the REN bit is set.
7.11.4.1 BD TABLE POINTER (RBASE, TBASE).
The RBASE and TBASE entries define
the starting location in the dual-port RAM for the set of BDs for receive and transmit func-
tioned. By selecting RBASE and TBASE entries for all SMCs, and by setting the W-bit in the
last BD in each BD list, the user may select how many BDs to allocate for the transmit and
receive side of every SMC. The user must initialize these entries before enabling the corre-
Table 7-12. SMC UART and Transparent
Address
Name
Width
Description
SMC Base + 00
RBASE
Word
Rx Buffer Descriptors Base Address
SMC Base + 02
TBASE
Word
Tx Buffer Descriptors Base Address
SMC Base + 04
RFCR
Byte
Rx Function Code
SMC Base + 05
TFCR
Byte
Tx Function Code
SMC Base + 06
MRBLR
Word
Maximum Receive Buffer Length
SMC Base + 08
RSTATE
Long
Rx Internal State
SMC Base + 0C
Long
Rx Internal Data Pointer
SMC Base + 10
RBPTR
Word
Rx Buffer Descriptor Pointer
SMC Base + 12
Word
Rx Internal Byte Count
SMC Base + 14
Long
Rx Temp
SMC Base + 18
TSTATE
Long
Tx Internal State
SMC Base + 1C
Long
Tx Internal Data Pointer
SMC Base + 20
TBPTR
Word
Tx Buffer Descriptor Pointer
SMC Base + 22
Word
Tx Internal Byte Count
SMC Base + 24
Long
Tx Temp
SMC Base + 28
First Word of Protocol Specific Area
SMC Base + 36
Last Word of Protocol Specific Area