z85230 ZiLOG Semiconductor, z85230 Datasheet - Page 105

• Manufacturer Part Number: z85230
• Description: Enhanced Serial Communications Controller
• Manufacturer: ZiLOG Semiconductor

PS005303-0907
RTS Problem Description
Ext/Status IUS
Figure 35
Ext/Status IP
The ESCC (Z80230/Z85230) contains a functional problem in Automatic RTS Deactiva-
tion (see
This mode is intended for SDLC applications where the RTS signal from the ESCC is used
to enable a line driver in multi-drop line communications.
Before the frame transmission, RTS is asserted by an
equals 0).
After the last data bit of a frame is sent, a Transmit Underrun interrupt is requested. A
Deactivate RTS
turn off the line driver after the multiple-frame packet is sent.
On the SCC, the processor must monitor the data line to ensure that the frame has been
sent before it issues the
On the ESCC, RTS can be programmed to deactivate automatically after the frame is sent.
If the following sequence is performed, additional monitoring is not required:
1. Enable Automatic RTS Deactivation (WR7’ bit 2 equals 1).
RCA IP
INT
Resetting highest IUS from lower priority interrupt clears the EOF (RCA) interrupt.
Figure 35. Resetting Highest IUS from Lower Priority
Figure 36
illustrates the procedure for resetting highest IUS.
command is issued (WR5 bit 1 equals 1) to deactivate the RTS signal to
on page 101).
Ext/Status
Interrupt
Deactivate RTS
DMA read
EOF
Reset Highest
command.
Ext/Status
IUS from
Handler
Activate RTS
Product Specification
command (ER5 bit1
Z80230/Z85230 Errata
Z85230/Z80230
100