
SCC/ESCC
User Manual
UM010903-0515 Interfacing the SCC/ESCC
61
Wait On Transmit Timing
This allows the use of a block move instruction to transfer the transmit data. In the case of the
Z80X30, /WAIT will go active in response to /DS going active, but only if WR8 is being accessed
and a write is attempted. In all other cases, /WAIT remains open-drain. In the case of the Z85X30,
/WAIT goes active in response to /WR going active, but only if the data buffer is being accessed,
either directly or via the pointers. The /WAIT pin is released in response to the falling edge of
PCLK. Details of the timing are displayed in Figure .
Care must be taken when using this function, particularly at slow transmission speed. The /WAIT
pin stays active as long as the transmit buffer stays full, so there is a possibility that the CPU may
be kept waiting for a long period.
Wait on Transmit Timing (ii)
/DS or /WR
to Tx Buffer
Tx Buffer Empty
/W//REQ
(=WAIT)
Empty
Full
/TRxC
/WAIT
SYNC Modes
PCLK
ASYNC Modes
Komentarze do niniejszej Instrukcji