Philips Semiconductors

Preliminary data

XA-G49

XA 16-bit microcontroller family

64K Flash/2K RAM, watchdog, 2 UARTs

2001 Jun 27

34

V2)

This variable represents the programmed width of the PSEN pulse as determined by the CR1 and CR0 bits or the CRA1, CRA0, and

ALEW bits in the BTRL register.

–

For a bus cycle with no ALE, V2 = 1 if CR1/0 = 00, 2 if CR1/0 = 01, 3 if CR1/0 = 10, and 4 if CR1/0 = 11. Note that during burst

mode code fetches, PSEN does not exhibit transitions at the boundaries of bus cycles. V2 still applies for the purpose of

determining peripheral timing requirements.

–

For a bus cycle with an ALE, V2 = the total bus cycle duration (2 if CRA1/0 = 00, 3 if CRA1/0 = 01, 4 if CRA1/0 = 10,

and 5 if CRA1/0 = 11) minus the number of clocks used by ALE (V1 + 0.5).

Example:

If CRA1/0 = 10 and ALEW = 1, the V2 = 4 – (1.5 + 0.5) = 2.

V3)

This variable represents the programmed length of an entire code read cycle with ALE. This time is determined by the CRA1 and

CRA0 bits in the BTRL register. V3 = the total bus cycle duration (2 if CRA1/0 = 00, 3 if CRA1/0 = 01, 4 if CRA1/0 = 10,

and 5 if CRA1/0 = 11).

V4)

This variable represents the programmed length of an entire code read cycle with no ALE. This time is determined by the CR1 and

CR0 bits in the BTRL register. V4 = 1 if CR1/0 = 00, 2 if CR1/0 = 01, 3 if CR1/0 = 10, and 4 if CR1/0 = 11.

V5)

This variable represents the programmed length of an entire data read cycle with no ALE. this time is determined by the DR1 and

DR0 bits in the BTRH register. V5 = 1 if DR1/0 = 00, 2 if DR1/0 = 01, 3 if DR1/0 = 10, and 4 if DR1/0 = 11.

V6)

This variable represents the programmed length of an entire data read cycle with ALE. The time is determined by the DRA1 and

DRA0 bits in the BTRH register. V6 = the total bus cycle duration (2 if DRA1/0 = 00, 3 if DRA1/0 = 01, 4 if DRA1/0 = 10,

and 5 if DRA1/0 = 11).

V7)

This variable represents the programmed width of the RD pulse as determined by the DR1 and DR0 bits or the DRA1, DRA0 in the

BTRH register, and the ALEW bit in the BTRL register. Note that during a 16-bit operation on an 8-bit external bus, RD remains low

and does not exhibit a transition between the first and second byte bus cycles. V7 still applies for the purpose of determining

peripheral timing requirements. The timing for the first byte is for a bus cycle with ALE, the timing for the second byte is for a bus

cycle with no ALE.

–

For a bus cycle with no ALE, V7 = 1 if DR1/0 = 00, 2 if DR1/0 = 01, 3 if DR1/0 = 10, and 4 if DR1/0 = 11.

–

For a bus cycle with an ALE, V7 = the total bus cycle duration (2 if DRA1/0 = 00, 3 if DRA1/0 = 01, 4 if DRA1/0 = 10,

and 5 if DRA1/0 = 11) minus the number of clocks used by ALE (V1 + 0.5).

Example:

If DRA1/0 = 00 and ALEW = 0, then V7 = 2 – (0.5 + 0.5) = 1.

V8)

This variable represents the programmed width of the WRL and/or WRH pulse as determined by the WM1 bit in the BTRL register.

V8 1 if WM1 = 0, and 2 if WM1 = 1.

V9)

This variable represents the programmed address setup time for a write as determined by the data write cycle duration (defined by

DW1 and DW0 or the DWA1 and DWA0 bits in the BTRH register), the WM0 bit in the BTRL register, and the value of V8.

–

For a bus cycle with an ALE, V9 = the total bus write cycle duration (2 if DWA1/0 = 00, 3 if DWA1/0 = 01, 4 if DWA1/0 = 10, and

5 if DWA1/0 = 11) minus the number of clocks used by the WRL and/or WRH pulse (V8), minus the number of clocks used by data

hold time (0 if WM0 = 0 and 1 if WM0 = 1).

Example: If DWA1/0 = 10, WM0 = 1, and WM1 = 1, then V9 = 4 – 1 – 2 = 1.

–

For a bus cycle with no ALE, V9 = the total bus cycle duration (2 if DW1/0 = 00, 3 if DW1/0 = 01, 4 if DW1/0 = 10, and

5 if DW1/0 = 11) minus the number of clocks used by the WRL and/or WRH pulse (V8), minus the number of clocks used by data

hold time (0 if WM0 = 0 and 1 if WM0 = 1).

Example:

If DW1/0 = 11, WM0 = 1, and WM1 = 0, then V9 = 5 – 1 – 1 = 3.

V10) This variable represents the length of a bus strobe for calculation of WAIT setup and hold times. The strobe may be RD (for data read

cycles), WRL and/or WRH (for data write cycles), or PSEN (for code read cycles), depending on the type of bus cycle being widened

by WAIT. V10 = V2 for WAIT associated with a code read cycle using PSEN. V10 = V8 for a data write cycle using WRL and/or WRH.

V10 = V7–1 for a data read cycle using RD. This means that a single clock data read cycle cannot be stretched using WAIT.

If WAIT is used to vary the duration of data read cycles, the RD strobe width must be set to be at least two clocks in duration.

Also see Note 4.

V11)

This variable represents the programmed write hold time as determined by the WM0 bit in the BTRL register.

V11 = 0 if the WM0 bit = 0, and 1 if the WM0 bit = 1.

V12) This variable represents the programmed period between the end of the ALE pulse and the beginning of the WRL and/or WRH pulse

as determined by the data write cycle duration (defined by the DWA1 and DWA0 bits in the BTRH register), the WM0 bit in the BTRL

register, and the values of V1 and V8. V12 = the total bus cycle duration (2 if DWA1/0 = 00, 3 if DWA1/0 = 01, 4 if DWA1/0 = 10, and 5

if DWA1/0 = 11) minus the number of clocks used by the WRL and/or WRH pulse (V8), minus the number of clocks used by data hold

time (0 if WM0 = 0 and 1 if WM0 = 1), minus the width of the ALE pulse (V1).

Example: If DWA1/0 = 11, WM0 = 1, WM1 = 0, and ALEW = 1, then V12 = 5 – 1 – 1 – 1.5 = 1.5.

V13) This variable represents the programmed data setup time for a write as determined by the data write cycle duration (defined by DW1

and DW0 or the DWA1 and DWA0 bits in the BTRH register), the WM0 bit in the BTRL register, and the values of V1 and V8.

–

For a bus cycle with an ALE, V13 = the total bus cycle duration (2 if DWA1/0 = 00, 3 if DWA1/0 = 01, 4 if DWA1/0 = 10, and

5 if DWA1/0 = 11) minus the number of clocks used by the WRL and/or WRH pulse (V8), minus the number of clocks used by

data hold time (0 if WM0 = 0 and 1 if WM0 = 1), minus the number of clocks used by ALE (V1 + 0.5).

Example:

If DWA1/0 = 11, WM0 = 1, WM1 = 1, and ALEW = 0, then V13 = 5 – 1 – 2 – 1 = 1.

–

For a bus cycle with no ALE, V13 = the total bus cycle duration (2 if DW1/0 = 00, 3 if DW1/0 = 01, 4 if DW1/0 = 10, and

5 if DW1/0 = 11) minus the number of clocks used by the WRL and/or WRH pulse (V8), minus the number of clocks used by

data hold time (0 if WM0 = 0 and 1 if WM0 = 1).

Example:

If DW1/0 = 01, WM0 = 1, and WM1 = 0, then V13 = 3 – 1 – 1 = 1.

3. Not all combinations of bus timing configuration values result in valid bus cycles. Please refer to the XA User Guide section on the External

Bus for details.

4. When code is being fetched for execution on the external bus, a burst mode fetch is used that does not have PSEN edges in every fetch

cycle. Thus, if WAIT is used to delay code fetch cycles, a change in the low order address lines must be detected to locate the beginning of

a cycle. This would be A3–A0 for an 8-bit bus, and A3–A1 for a 16-bit bus. Also, a 16-bit data read operation conducted on a 8-bit wide bus

similarly does not include two separate RD strobes. So, a rising edge on the low order address line (A0) must be used to trigger a WAIT in

the second half of such a cycle.