Zilog Z80230 Instrukcja Użytkownika Strona 11

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SCC/ESCC
User Manual
UM010903-0515 General Description
4
Improved functionality to ease sending back-to back frames
Automatic SDLC opening Flag transmission*
Automatic Tx Underrun/EOM Latch reset in SDLC mode*
Automatic /RTS deactivation*
TxD pin forced “H” in SDLC NRZI mode after closing flag*
Complete CRC reception*
Improved response to Abort sequence in status FIFO
Automatic Tx CRC generator preset/reset
Extended read for write registers*
Write data setup timing improvement
Improved AC timing:
Three to 3.5 PCLK access recovery time.
Programmable /DTR//REQ timing*
Elimination of write data to falling edge of /WR setup time requirement
Reduced /INT timing
Other features include:
Extended read function to read back the written value to the write registers*
Latching RR0 during read
RR0, bit D7 and RR10, bit D6 now has reset default value
Some of the features listed above are available by default, and some of them (features with “*”)
are disabled on default.
ESCC (Enhanced SCC) is pin and software compatible to the CMOS version, with the following
additional enhancements.
Deeper transmit FIFO (4 bytes)
Deeper receive FIFO (8 bytes)
Programmable FIFO interrupt and DMA request level
Seven enhancements to improve SDLC link layer supports:
Automatic transmission of the opening flag
Automatic reset of Tx Underrun/EOM latch
Deactivation of /RTS pin after closing flag
Automatic CRC generator preset
Complete CRC reception
TxD pin automatically forced high with NRZI encoding when using mark idle
Status FIFO handles better frames with an ABORT
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