17
17-3
Rev.1.0
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(5) Byte low write/byte low enable (BLW/BLE)
The pin function is changed using the Bus Mode Control Register (BUSMODC).
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When BUSMOD = 0, Byte Low Write (BLW) is selected, indicating that valid data is transferred on
the lower byte side (DB8-DB15) of the data bus during external write access. This output is held
high during an external read cycle.
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When BUSMOD = 1, Byte Low Enable (BLE) is selected, indicating that valid data is transferred
on the upper byte side (DB8-DB15) of the data bus during external access. This output is held
high when accessing an internal function.
(6) Data bus (DB0-DB15)
This is a 16-bit data bus used to access an external device.
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(7) System clock/write (BCLK/WR)
The pin function is changed using the Bus Mode Control Register (BUSMODC).
When BUSMOD = 0, System Clock (BCLK) is selected, generating the system clock needed for
the synchronized design of external devices. When the CPU clock is 40 MHz, a 20 MHz clock is
output from BCLK. When not using the BCLK/WR function, this pin can be used as P70 by setting
the P7 Operation Mode Register P70MOD bit to 0.
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BUSMOD = 1, Write (WR) is selected, indicating that valid data is transferred on the data bus
during external write access. This output is held high during an external read cycle and when
accessing an internal function.
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(8) Wait (WAIT)
When the 32172/32173 started an external bus cycle, it automatically inserts wait cycles while
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the WAIT signal is asserted. For details, see Chapter 18, "Wait Controller." When not using the
WAIT function, this pin can be used as P71 by setting the P7 Operation Mode Register P71MOD
bit to 0.
For external access, one or m ore wait states are always inserted. Therefore, access to an
external device incurs at least one wait state (total 2 BCLK cycles).
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(9) Hold control (HREQ, HACK)
A hold state refers to a condition where bus access is halted and all of the bus interface related
pins are placed in the high-impedance state. While in a hold state, any external bus master can
use the system bus to transfer data.
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A hold state is entered into by pulling the HREQ pin input. After the hold request is accepted, the
EXTERNAL BUS INTERFACE
17.1 External Bus Interface Related Signals
Содержание 32172
Страница 20: ... This is a blank page 16 ...
Страница 21: ...1 1 Overview 1 2 Block Diagram 1 3 Pin Functions 1 4 Pin Layout CHAPTER 1 CHAPTER 1 OVERVIEW ...
Страница 44: ...1 1 24 Rev 1 0 This is a blank page Overview 1 4 Pin Layout ...
Страница 58: ...2 2 14 Rev 1 0 This is a blank page CPU 2 6 Data Formats ...
Страница 122: ...4 4 26 Rev 1 0 This is a blank page EIT 4 13 Precautions on EIT ...
Страница 200: ...7 7 6 Rev 1 0 This is a blank page RESET 7 4 Precautions to Be Taken Immediately after Reset ...
Страница 240: ...8 8 40 Rev 1 0 This is a blank page INPUT OUTPUT PORTS AND PIN FUNCTIONS 8 5 Precautions on Input Output Ports ...
Страница 298: ...9 9 58 Rev 1 0 This is a blank page DMAC 9 4 Precautions on Using DMAC ...
Страница 416: ...10 10 118 Rev 1 0 This is a blank page INPUT OUTPUT TIMERS 10 6 TOM Output Related 16 bit Timers ...
Страница 658: ...14 14 16 Rev 1 0 REAL TIME DEBUGGER RTD 14 4 Typical Connection with the Host This is a blank page ...
Страница 718: ...16 16 16 Rev 1 0 This is a blank page D A CONVERTERS 16 3 Functional Description of the D A Converters ...
Страница 766: ...18 18 22 Rev 1 0 WAIT CONTROLLER 18 3 Typical Operation of the Wait Controller This is a blank page ...
Страница 776: ...19 19 10 Rev 1 0 RAM BACKUP MODE 19 4 Exiting RAM Backup Mode Wakeup This is a blank page ...
Страница 777: ...CHAPTER 20 CHAPTER 20 OSCILLATION CIRCUIT 20 1 Oscillator Circuit 20 2 Clock Generator Circuit ...
Страница 782: ...20 20 6 Rev 1 0 OSCILLATION CIRCUIT 20 2 Clock Generator Circuit This is a blank page ...
Страница 856: ...23 23 26 Rev 1 0 This is a blank page ELECTRICAL CHARACTERISTICS 23 6 AC Characteristics ...
Страница 857: ...24 1 A D Conversion Characteristics CHAPTER 24 CHAPTER 24 STANDARD CHARACTERISTICS ...
Страница 859: ...Appendix 1 1 Dimensional Outline Drawing APPENDIX 1 APPENDIX 1 MECHANICAL SPECIFICATIONS ...
Страница 861: ...Appendix 2 1 M32R E Instruction Processing Time APPENDIX 2 APPENDIX 2 INSTRUCTION PROCESSING TIME ...
Страница 865: ...Appendix 3 1 Precautions about Noise APPENDIX 3 APPENDIX 3 PRECAUTIONS ABOUT NOISE ...