# How can I write a 64 bit number in Control Register from Python **URL:** \ **Category:** Support\ **Created:** [April 27, 2023, 9:42am UTC](https://discuss.pynq.io/t/how-can-i-write-a-64-bit-number-in-control-register-from-python/5519 "2023-04-27T09:42:43Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![davide-giacomini](https://sea1.discourse-cdn.com/flex019/user_avatar/discuss.pynq.io/davide-giacomini/32/3137_2.png) [@davide-giacomini](https://discuss.pynq.io/u/davide-giacomini)\ **Post date:** [April 27, 2023, 9:42am UTC](https://discuss.pynq.io/t/how-can-i-write-a-64-bit-number-in-control-register-from-python/5519/1 "2023-04-27T09:42:43Z")
Hello everyone, I am writing a Python interface between the ARM and the FPGA of my Pynq Z2 and I have to write in the Control Register some scalars of 64 bits. For now I found a workaround like this: ```auto MSB_mu_cpu = Fxp(mu_cpu).like(d_fixed_t).bin()[:32] LSB_mu_cpu = Fxp(mu_cpu).like(d_fixed_t).bin()[32:] MSB_DELTA_T = Fxp(DELTA_T).like(d_fixed_t).bin()[:32] LSB_DELTA_T = Fxp(DELTA_T).like(d_fixed_t).bin()[32:] lin_ip.write(0x10, buffer_X_FPGA.physical_address) lin_ip.write(0x1c, int(LSB_mu_cpu, 2)) lin_ip.write(0x20, int(MSB_mu_cpu, 2)) lin_ip.write(0x28, int(LSB_DELTA_T, 2)) lin_ip.write(0x2c, int(MSB_DELTA_T, 2)) ``` In this code, I firstly get the binary string of te variables already converted in fixed points and then I write manually the LSB and MSB bits. Although, when I have to read from memory I will get still the MSB and LSB separately, and this creates some issues when riconverting them. For reference, I am using this lbrary for fixed ponints: [GitHub - francof2a/fxpmath: A python library for fractional fixed-point (base 2) arithmetic and binary manipulation with Numpy compatibility.](https://github.com/francof2a/fxpmath). Thank you in advance, Davide ---
**Author:** ![briansune](https://sea1.discourse-cdn.com/flex019/user_avatar/discuss.pynq.io/briansune/32/3087_2.png) [@briansune](https://discuss.pynq.io/u/briansune)\ **Post date:** [April 27, 2023, 11:50am UTC](https://discuss.pynq.io/t/how-can-i-write-a-64-bit-number-in-control-register-from-python/5519/2 "2023-04-27T11:50:01Z")
@davide-giacomini Zynq ARM A9 is 32bit so even you need 64bit ctrl TX, should it split it into at least 2 cycle of combine 64 bit data? So instead of considering it as 1 64 bit TX the back-end ends up with two 32bit join data. ENJOY~ ---
**Author:** ![marioruiz](https://sea1.discourse-cdn.com/flex019/user_avatar/discuss.pynq.io/marioruiz/32/2177_2.png) [@marioruiz](https://discuss.pynq.io/u/marioruiz)\ **Post date:** [April 27, 2023, 1:35pm UTC](https://discuss.pynq.io/t/how-can-i-write-a-64-bit-number-in-control-register-from-python/5519/3 "2023-04-27T13:35:04Z")
Hi @davide-giacomini, For read, you can request a longer read, `length=8` > And for write, you can pass the data as bytes > Mario ---
**Author:** ![briansune](https://sea1.discourse-cdn.com/flex019/user_avatar/discuss.pynq.io/briansune/32/3087_2.png) [@briansune](https://discuss.pynq.io/u/briansune)\ **Post date:** [April 27, 2023, 3:45pm UTC](https://discuss.pynq.io/t/how-can-i-write-a-64-bit-number-in-control-register-from-python/5519/4 "2023-04-27T15:45:32Z")
@marioruiz read(self, offset=0, length=4, word\_order=“little”): So does this mean we could read back as either little-endian or big-endian in MMIO API? But it is still in a byte form no matter how. How about write ← could we write as either little-endian or big-endian in MMIO API? Thank you ENJOY~ ---
**Author:** ![marioruiz](https://sea1.discourse-cdn.com/flex019/user_avatar/discuss.pynq.io/marioruiz/32/2177_2.png) [@marioruiz](https://discuss.pynq.io/u/marioruiz)\ **Post date:** [April 27, 2023, 5:55pm UTC](https://discuss.pynq.io/t/how-can-i-write-a-64-bit-number-in-control-register-from-python/5519/5 "2023-04-27T17:55:20Z")
Hi Brian, > So does this mean we could read back as either little-endian or big-endian in MMIO API? > But it is still in a byte form no matter how. Only at the word level (32-bit). The return would be an `int` > How about write ← could we write as either little-endian or big-endian in MMIO API? No, this capability is not part of the write. If you want to write more than 32-bit, you need to pass the data as `bytes` Mario ---
**Author:** ![marioruiz](https://sea1.discourse-cdn.com/flex019/user_avatar/discuss.pynq.io/marioruiz/32/2177_2.png) [@marioruiz](https://discuss.pynq.io/u/marioruiz)\ **Post date:** [April 27, 2023, 5:55pm UTC](https://discuss.pynq.io/t/how-can-i-write-a-64-bit-number-in-control-register-from-python/5519/6 "2023-04-27T17:55:25Z")