Chip Selects
5-4
Am186™CC/CH/CU Microcontrollers User’s Manual
5.5
OPERATION
5.5.1
Usage
Note: Before using the chip selects, ensure multiplexed pins are configured to reflect the
use of the chip selects and not other functionality (see Table 5-1 on page 5-3).
Except for the UCS chip select, which is active on reset, chip selects are not activated until
the associated register is written (not when it is read). All these signals are three-stated
during a bus-hold condition and during reset to allow an external bus master to drive these
signals directly.
■
To use the Upper Memory Chip Select (UCS), configure the following UMCS register
options:
– Lower boundary of UCS (LB bit field)
– AD bus disable (DA bit)
– DRAM enable (UDEN bit)
– Data bus width (USIZ bit)
– External Ready mode (R2 bit)
– Wait state value (R1 and R0 bits)
UCS is active on reset.
■
To use the Lower Memory Chip Select (LCS), configure the following LMCS register
options:
– Upper boundary of LCS (UB bit field)
– AD bus disable (DA bit)
– DRAM enable (UDEN bit)
– Data bus width (LSIZ bit)
– External Ready mode (R2 bit)
– Wait state value (R1 and R0 bits)
LCS is activated when the LMCS register is written.
■
To use the Peripheral Chip Select (PCS), configure the following options in the PACS
and MPCS registers:
– Base address (BA bit field in PACS)
– External Ready mode (R2 bit in PACS)
– Wait state value (R0, R1, and R3 bits in PACS)
– PCS mapped to memory or I/O (MS bit in MPCS)
– Memory data bus width for all non-UCS and non-LCS memory (OMSIZ bit in MPCS)
– I/O data bus width (IOSIZ bit in MPCS)
The PCS chip selects are activated after both the PACS and MPCS registers are written.
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...