System Overview
3-14
Am186™CC/CH/CU Microcontrollers User’s Manual
SRDY [PIO35]
STI
Synchronous Ready indicates to the microcontroller that the
addressed memory space or I/O device will complete a data
transfer. The SRDY pin accepts an active High input
synchronized to CLKOUT.
Using SRDY instead of ARDY allows a relaxed system timing
because of the elimination of the one-half clock period required
to internally synchronize ARDY. To always assert the ready
condition to the microcontroller, tie SRDY High. If the system
does not use SRDY, tie the pin Low to yield control to ARDY.
WHB
WLB
—
—
O
O
Write High Byte and Write Low Byte indicate to the system
which bytes of the data bus (upper, lower, or both) participate in
a write cycle. In 80C186 microcontroller designs, this information
is provided by BHE, AD0, and WR. However, by using WHB and
WLB, the standard system interface logic and external address
latch that were required are eliminated.
WHB is asserted with AD15–AD8. WHB is the logical AND of
BHE and WR. This pin is three-stated with a pullup during bus-
hold or reset conditions.
WLB is asserted with AD7–AD0. WLB is the logical AND of AD0
and WR. This pin is three-stated with a pullup during bus-hold
or reset conditions.
WR [PIO15]
O
Write Strobe indicates to the system that the data on the bus is
to be written to a memory or I/O device. WR is three-stated with
a pullup during bus-hold or reset conditions.
CLOCKS/RESET/WATCHDOG TIMER
CLKOUT —
O
Clock Output supplies the clock to the system. Depending on
the values of the CPU mode select pinstraps, {CLKSEL1} and
{CLKSEL2}, CLKOUT operates at either the PLL frequency or
the source input frequency during PLL Bypass mode. (See
Table 3-5 on page 3-7.) CLKOUT remains active during bus-hold
or reset conditions.
The DISCLK bit in the SYSCON register can be set to disable
the CLKOUT signal. Refer to the
Am186™CC/CH/CU
Microcontrollers Register Set Manual
, order #21916.
All synchronous AC timing specifications not associated with
SSI, HDLCs, UARTs, and the USB are synchronous to CLKOUT.
Table 3-7
Signal Descriptions (Continued)
Signal Name
1
Multiplexed
Signal(s)
Type Description
Summary of Contents for Am186 CC
Page 1: ...Am186 CC CH CU Microcontrollers User s Manual Order 21914B...
Page 4: ...iv Am186 CC CH CU Microcontrollers User s Manual...
Page 18: ...Table of Contents xviii Am186 CC CH CU Microcontrollers User s Manual...
Page 24: ...Introduction xxiv Am186 CC CH CU Microcontrollers User s Manual...
Page 40: ...Architectural Overview 1 16 Am186 CC CH CU Microcontrollers User s Manual...
Page 86: ...System Overview 3 36 Am186 CC CH CU Microcontrollers User s Manual...
Page 92: ...Emulator Support 4 6 Am186 CC CH CU Microcontrollers User s Manual...
Page 112: ...DRAM Controller 6 8 Am186 CC CH CU Microcontrollers User s Manual...
Page 134: ...Interrupts 7 22 Am186 CC CH CU Microcontrollers User s Manual...
Page 186: ...Programmable I O Signals 9 8 Am186 CC CH CU Microcontrollers User s Manual...
Page 200: ...Watchdog Timer 11 6 Am186 CC CH CU Microcontrollers User s Manual...
Page 232: ...Asynchronous Serial Ports UARTs 13 24 Am186 CC CH CU Microcontrollers User s Manual...
Page 242: ...Synchronous Serial Port SSI 14 10 Am186 CC CH CU Microcontrollers User s Manual...
Page 264: ...High Level Data Link Control HDLC 15 22 Am186 CC CH CU Microcontrollers User s Manual...
Page 332: ...Universal Serial Bus USB 18 34 Am186 CC CH CU Microcontrollers User s Manual...
Page 348: ...Register Summary A 16 Am186 CC CH CU Microcontrollers User s Manual...
Page 376: ...Index Index 18 Am186 CC CH CU Microcontrollers User s Manual...