MC68HC58 Motorola, MC68HC58 Datasheet - Page 51

• Manufacturer Part Number: MC68HC58
• Description: Data Link Controller
• Manufacturer: Motorola

4.2.1.3 Minimum Time Requirements
4.2.1.4 Motorola Microcontroller Data Transfers
MC68HC58
TECHNICAL DATA
The host MCU can read only the status byte, or can read the status byte followed by
a read of a data byte (the data read automatically flushes the associated data byte
from the RxFIFO buffer). There is no specified maximum time between reading of a
status byte and reading of a data byte, but correct status of the RxFIFO is guaranteed
only for 1 s.
The DLC allows a host to write contiguous frame bytes to the TxFIFO buffer without
intervening command bytes, provided that the first and last data bytes are accompa-
nied by “load as first byte of transmit data”, “load as last byte of transmit data”, or “load
as first and last byte of transmit data” command bytes. A data, configuration, or null
byte need not immediately follow the associated command, but must be the next byte
transferred to the DLC. The command byte is acted upon when the subsequent byte
is written into the DLC.
Minimum time constraints appear on certain sequences of operations. Table 4-2
shows the minimum time required between these operations. The left column shows
initial operations; the top row, subsequent operations.
Many Motorola microcontroller families, including the M68HC11, M68HC16, and
M68300 series MCUs, can generate synchronous ADDR0, DATA, CLK and R/W sig-
nals.
For example, host MCUs based on M68HC11 microcontrollers can use instructions
that load 16-bit double accumulator D from two consecutive byte addresses (LDD),
and store accumulator content into two consecutive byte addresses (STD).
Host MCUs based on M68HC16 and M68300 microcontrollers can use the dynamic
bus sizing capability to automate the transfer of 16-bit data to and from an 8-bit port.
NOTES:
Data/Config
Command
1. During block transfers only.
2. Status valid for 1 s
Status
Write
Write
Read
Read
Data
Table 4-2 Minimum Time Between Operations
Not allowed
Command
DATA LINK CONTROLLER OPERATION
Write
3 s
3 s
0
Data/Config
Not allowed
Not allowed
Write
3 s
0
1
Not allowed
Status
Read
3 s
0
0
2
Not allowed
Not allowed
Not allowed
Read
Data
0
MOTOROLA
4-7